Same problem here. Cant Publish/Update. Endless turning Arrow in WP Update Button.
German WP 4.9.6., Custom theme. Lots of Custom Post Types.
Reverting to 5.6 solves the problem and runs faster.
Update to WP 4.9.7 -> no change.
BTW: Thanks Elliot for your outstanding work over the last years and your wonderful pro version which is easyly the most important plugin for me.
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