Order of draggable entries and assets won't save Hello Craft Community,

I have a site which has just over 300 entries but most entries have several asset fields, entry fields, or complex matrices.

My problem is that when on an existing entry, I cannot drag-to-reorder any items in an asset or entry field-type. The CP will let me reorder, but saving the entry does not retain my new ordering.

There are no console errors related to this problem, so I'm looking for advise on where to start troubleshooting.

Thanks!

Edit: additional note that my PHP runtime config variables seem to be in order, 256M memory, 3000 max_input_vars, etc.
From your description, if I had to guess, you're running into a php.ini max_input_vars, post_max_size or some other related environmental limitation.  I'd try bumping those as a starting point for debugging.