I guess you can get a bit of an idea of what this is like by listening to French people speak English. French doesn’t have phonemic syllable stress like English does and so French people often make mistakes with this. For a native English speaker the syllable stress is an integral part of the word and being phonemic it actually distinguishes between two words that otherwise sound the same. The commonest category of this would be words that change between verb and noun depending on the stress, like “reject”, “protest”, “transfer” etc. And there are other minimal pairs like “insight” vs “incite”.

The native English (many other Indo-European languages also have similar systems) speaker is very unlikely to make a pronunciation mistake in this manner but even very accomplished francophone speakers of English struggle with it even after being corrected.

For example here’s French cabinet minister Bruno Le Maire pronouncing “damages” as “daMAges” https://youtu.be/qKWFsg5uHKo