I have set up IMAP for gmail on Kmail 5.4 on opensuse tumbleweed, senting the sync limit to 2,000 emails. Everything is good except user specified folders, for example i have set up category:primary and the most recent email is from 2007 whilst the equivelent inbox has the most recent with the oldest being 2013. Have tried re-syncing, restarting, toggling the "include in IMAP" on gmail and again re-syncing. Nothing changes.

update: after several hours and recieving new emails I have the most recent new mail - then a gap - then emails starting from 2007.

I have also posted the bug on gmail product forum, thanks for any help/advice or confirmation of the problem.

[solved] (by google team) required deleting account, deleted akonadi data folder and then re-setup.
I presume it was caused by setting up the gmail folders after having set up the client, or possibly having applied the 2,000 limit later.