Apologies if this has already been posted elsewhere (I couldn't find anything) but I recently upgraded/renewed my subscription to Web Designer Pro (16) from an earlier version of 365 (purchased 2016). When I am trying to edit some web pages I created in the earlier version, I am getting the error message:

Internal program error 1599.k.sy.up

It pops up every few seconds, even if I'm not actually doing anything.

Anyone know what could be causing it? I'm using Windows 10 Pro 64-bit, version 1803, on a Surface Pro with 8 gigs of RAM. Intel Core i5 processor.

Thanks in advance for your help.

Debbie