Lag with Network XP/Win10

I know XP isn't supported but my setup needs it. I'm file sharing it with two win10 machine via LAN cable.
It worked fine for years but I had to change a hard drive (in win10) and also tested a new clone on XP worked ok, then restored the original drive.
Now, sometimes with XP there is a lag of about a minute opening Explorer or after clicking a jpg before it opens.
I've tried rebooting and turning Network off and back on.
It isn't consistent, and can be ok but always, eventually the lag is back. Sometimes even on the next attempt.
Has anyone else had this sort of thing and found a reason or a fix?
Is there anything I can do to try and find the problem ?
Thanks.

I know this may sound stupid - but did you try running everything/opening it as an administrator rather than a simple double-click? That's what I do when I need to use incompatible apps with my Win10...

I didn't but I'm not sure how to open/run as admin. Nothing on a r-click shows that.
With the lag opening explorer (Win-E) I have the LAN cable ready to disconnect, trying to prove if that changes anything.. It's difficult as the second Win-E can work. Or not.. sometimes there's xxx number of explorers all at once after the delay.