I rarely use 7zip, but when used, never encountered such issue with it. I believe such programs use crc to detect deflation problems, so there should be an error reported (however my 7zip does not inform that the file was extracted successfully, either).
Once I had similar problem with another program (don't remember which one), but finally found a root cause (gave it a second try)- disk full
. Of course an appropriate message popped up, but I lost it during windows switching and closing program
. Of course file was smaller than it should. Some programs leave partially uncompressed files on disk in such case, but some remove them- maybe try to check how 7zip behaves under similar conditions.
Btw. I use linux (connected to internet) utility to compress files.
Art