After using a filter with imapflagging all sieve dependend functions like vacation and the other filters are defect, the sieve script cannot be compiled anymore and the SOGo-Log shows entries like

Feb 09 10:23:18 sogod [11721]: [ERROR] <0x0980C1F8[SOGoMailAccount]:0> Could not upload Sieve script: {RawResponse = "{ok = NO; reason = \"sogo: line 1: error: require command: unknown Sieve capability 'imapflags'.
sogo: line 20: error: unknown command 'addflag' (only reported once at first occurence).
sogo: error: validation failed.
\"; }"; result = NO; }

This error was found on a Dovecot-1.2-Machine.
Dovecot uses only the Rfc-conform "imap4flags" module, the cmusieve-compatible "imapflags"-module has to be enabled by adding
sieve_extensions = +imapflag
to the dovecot-configuration.

But, managesieve shows up its capabilities and tells sogo, it uses imap4flags.
So, it would be a solution to test for the capabilities and use imapflags or imap4flags (since it is part of the newer RFC of sieve and imapflags is marked as deprecated).

Other solution: put a switch like "use_cmusieve" (YES/NO) into the SOGo-config so SOGo knows, which modules are available.

Side action: the incident 0000676 could be (partly) solved - without cmusieve (which cannot handle the date-extension)