The short answer
Four things break, in roughly this order of how often they bite: word order, because most Indian languages put the verb at the end and English does not; glyph rendering, because Indic scripts fail silently when the renderer lacks the right font; line length, because translated text is usually longer; and register, because machine translation flattens formality that Indian languages encode in the verb.
Translate whole segments rather than words, export a real test clip and look at the downloaded file rather than the preview, loosen your caption pacing after translating, and read the result against the original audio. That covers all four.
Word order is the structural problem
English is subject-verb-object: "I watched the video." Hindi, Tamil, Telugu, Bengali, Kannada and most other Indian languages are subject-object-verb: the verb goes at the end of the clause.
This is why word-by-word caption translation fails completely for these pairs. Translate each word in place and keep its timing, and you get correct vocabulary in the wrong order — which is not a sentence, and reads as broken to any native speaker regardless of how accurate the individual words are.
Tools do it anyway because it solves a real problem cheaply. If each word keeps its original timestamp, the captions stay perfectly synced with zero extra work. Segment-level translation forces you to give that up: a translated caption cannot have trustworthy per-word timing, because the words do not correspond one-to-one.
The honest resolution is to keep line-level timing, drop per-word timing on translated captions rather than fabricating it, and hold on to the measured source words so nothing is lost. A timestamp that is honestly coarse is better than one that is precisely wrong.
Indic scripts fail silently, which is the dangerous part
This is the failure that catches people out, because nothing errors.
Devanagari, Tamil, Telugu, Bengali and the rest need glyph shaping. Consonants combine into conjunct clusters, vowel marks attach above, below and around the base character, and the drawn form of a character depends on its neighbours. A video renderer without a font that supports this does not stop and tell you. It substitutes a default font and draws empty boxes, disconnected fragments, or — worst — text that looks plausible with the conjuncts quietly wrong.
The expensive version is the inconsistent one: correct in the browser preview, broken in the exported file. The browser and the encoding server resolve fonts independently, so your browser having a suitable font says nothing about the machine doing the render.
So the test is always the same, for any tool: export a real clip with Indic text in it and open the downloaded video. Not the preview. If the glyphs survive the round trip, the tool ships its own fonts and names them explicitly to the renderer rather than trusting the host machine. If they do not, nothing else about the tool matters for your use case.
Length and vertical space
Translated text is usually longer than its source, and captions live in a fixed amount of screen and time. A line that fitted comfortably in English can overflow the frame or flash past unread once translated, without a single word being wrong.
Indic scripts add a second dimension to this. Devanagari and Bengali put vowel marks above and below the baseline, so a line needs more vertical room than Latin text at the same point size. Tamil and Telugu have tall, round glyph forms with similar demands. Cramping the line spacing is what makes Indic captions look broken even when every character is correct — and it is a styling mistake, not a translation one.
Fix it with pacing rather than by rewriting captions. Fewer words per line and more lines on screen gives the translated text room. Do this after translating, watching the clip once at normal speed and looking specifically for lines that no longer fit.
Register, and your own vocabulary
Hindi and most Indian languages encode formality grammatically — the verb form itself tells a listener how the speaker regards them. Machine translation tends to flatten everything to one middle register, usually a formal one.
The effect is subtle and costly. A casual, joking English line arrives in Hindi sounding like a textbook. Nothing is mistranslated; the whole relationship with your audience has just shifted. For creator video, where the tone is often the entire product, this matters more than an occasional wrong noun.
The other predictable loss is your own vocabulary. Product names, brand names and technical terms get helpfully translated into common nouns unless you catch them. Make a list of the terms that must not be translated and check them specifically after every translation pass — it is the same five or ten words every time, so it takes seconds once you know them.
Both of these are only catchable by reading the translation while hearing the original. A line can be grammatically perfect and say something you did not mean, and only the comparison surfaces it.
A checklist before you export
Correct the source transcript before translating. An error in the source is translated faithfully into an error in the target, and it is far cheaper to fix once.
Check your untranslatable terms — names, brands, product vocabulary.
Watch the clip once at normal speed, looking only for lines that are now too long or too fast to read.
Export a test render and open the actual file to confirm the script drew correctly.
Then publish. The whole pass is a few minutes on a short clip, and it is the difference between captions a native speaker reads and captions they scroll past.