I would check in Preferences > Auto-assembling (especially Transfer numbers to segments and Fuzzy match auto-correction, try with these OFF).
(At least some) Auto-assembling settings are also used for (fuzzy) match transferring.
Note to Igor: Especially, I don't think Fuzzy match auto-correction should be enabled by default…
Additionally, if these are repeated segments, also try disabling numbers and non-translatables from Auto-propagations settings.
Here is Anthony's info in a better legible form. I'll also attach the great PDF with updated techniques. And I'll file to requests for enhancements.