FTBFS on all recent uploads

[Joachim Zobel <jz-2017@heute-morgen.de>]

Hi.

I have a FTBFS on all uploads after the end of the freeze. Example:
https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/gap-aclib.html

All these packages had been changed to compat 13. Unfortunately I have
no idea why I get these. I can see two logs of successful builds and a
diff for them. At the end of each log I find reproducible ➤ FTBFS, so
this probably is because my build fails to be reproducible. However the
only diff I see is the diff between the build logs. 

Any hints on what to do about these would be helpful.

Thanks,
Joachim