What happens if a table has a trigger, and there is some problem when updating the record? Is the entire trigger supposed to be embedded in a transaction, which will undo any changes done in the trigger?

More specifically, my problem is the following. I have a material reception / material delivery form, which will update the current stock - updating is done through a trigger. Under certain circumstances, the user gets an error message, "Update conflict", with the option "Retry?" I still have to investigate why exactly the error appears, and what exactly the framework (VFX) does, but I have the impression that the Retry will do a forced update.

In this case, the data gets saved, but the stock is out of synch, meaning that there was some problem with the trigger.

Of course, I will have to investigate and debug the framework code (the error seems to be easy to reproduce). But I also wanted to see if anybody could give me a clue about trigger handling in general, as explained in the first paragraph.