[Dovecot] zlib plugin maildir broken ?/ Cached message size smaller than expected

Hi Timo, by having errors like

Cached message size smaller than expected and Maildir filename has wrong S value and Corrupted index cache file

in dove 2.1.8

i can reproduce the problem with tb 14 with 2 nat machines connected to the same server

the problem relates with create new folder then copy some uncompressed and compressed mail to it, the i.e open it by other client

sometime this happens at once , sometime after a few copy actions

however thunderbird ,then errors above apear, sometimes no mail is shown, sometimes only uncompressed or only compressed

so funktion read both formats gets lost somehow any idea, you need a better debug ?

Best Regards MfG Robert Schetterer