[geek1011]

For anyone having issues with read-only overridden dictionaries being overwritten, use this temporary patch for now (4.20.14622):

Never sync dictionaries:
- Enabled: no
- ReplaceBytes: {Offset: 0x6108B0, FindH: 0CD5, ReplaceH: 0CE0} #permissions
- ReplaceBytesNOP: {Offset: 0x61089A, FindH: FFF68DAE} #size
- ReplaceBytesNOP: {Offset: 0x610878, FindH: 3FF49EAE} #isSynced

And a multi-version one (4.20.14601+) (kobopatch v0.15.0+):

Never sync dictionaries:
- Enabled: no
- BaseAddress:  {Sym: "SyncDictionariesCommand::prepareDownloadList()"}
- ReplaceBytes: {Offset: 1048, FindH: 0CD5,     ReplaceH: 0CE0}         #permissions
- ReplaceBytes: {Offset: 1026, FindH: FFF68DAE, ReplaceInstNOP: true}   #size
- ReplaceBytes: {Offset:  992, FindH: 3FF49EAE, ReplaceInstNOP: true}   #isSynced

I think I've almost figured out why this is happening.

Thanks to Alanon for helping to debug this!