Found a lot of such messages in ARCHMGR.OUT:
Mai 26 03:07:09 ERROR TRACE at ModelArchDBImp.cc(1532): ModelArchDBImp::submitEvent ( model_h=0x4f251d, type=0x82105a, utime: 1464224828 ): Maximum vardata string length exceeded
The mentioned Event is:
0x82105a (Configuration Manager - A configuration change notification was received )
The Archive Manager doesn't store these events, when the problem happens.
This happens if the number of changed lines is very large.
ArchMgr "Maximum vardata string length exceeded" error when storing very large event data, causing event not to be logged.