Freron MailMate

MailMate appears to canonicalize an IMAP keyword to an old casing even after the tags mapping and Dovecot keyword mappings are lowercase.

All of my IMAP flags are lowercase, with uppercase display names. For instance, in Tags.plist the tag has:

displayName = Holidays
serverKeyword = holidays

Checking my server, Dovecot keyword files also map the relevant mailbox keyword to lowercase in dovecot-keywords:

11 holidays

I removed all instances of this flag on emails in my accounts, then verified via Dovecot search/fetch that were no existing messages with either keyword. But when I apply the MailMate tag, Activity Viewer logs show it's sending the uppercase version. This is apparent in the app too, I initially see \holidays in the raw flags column and the immediately it changes to \Holidays.

3:55:14 Handling reply
13:55:14 Running action
13:55:14 Handling request
13:55:14 Ready to run action (type: 1005, retry count: 0)
13:55:14 C: F26 NOOP
13:55:14 S: F26 OK NOOP completed (0.001 + 0.000 secs).
13:55:14 Storing flags (enable: 'holidays', disable: '')
13:55:14 C: F27 UID STORE 5826 +FLAGS.SILENT (Holidays)
13:55:14 S: * 18 FETCH (UID 5826 MODSEQ (11776))
13:55:14 S: F27 OK Store completed (0.001 + 0.000 secs).
13:55:14 C: F28 UID FETCH 5826 (FLAGS)
13:55:14 S: * 18 FETCH (UID 5826 FLAGS (\Seen Holidays))
13:55:14 S: F28 OK Fetch completed (0.001 + 0.000 secs).
13:55:14 Completed action (1005). Observed read/write timeouts: 8/8

MailMate's action layer says it is enabling lowercase holidays, but the emitted IMAP STORE command sends uppercase Holidays.

I've tried rebuilding the database, as well as removing and re-adding the tags, but nothing seems to work.

Is there anything I can look at that might be causing this strange caching issue?