Mac mini slow/fails sending videos to iPhone 16 Pro Max

Hi

Why does it take so long for my Mac mini to send 3 videos (<400mb) to my iPhone 16 Pro Max and then it fails?

Sometimes sending multiples succeed but alway longer than sending separately.

When sent singly they each succeed in ~20seconds.

Tho in each the export races to about 50% then suddenly slows.

But when I send from iPhone to Mac mini there is no slowdown, as it used to be the other way.

Since iPhone-> Mac is good, I feel it's a probably a Mac mini problem, and that's why I'm asking here.

Does some cache need emptying? Why the slows?

Royks