OK, did some testing.
I run a local on AMMPS on Mac. I tried PHP 5.6, 7.0 and 7.1 and my live runs 7.0 and all were having the same issue.
I found out that you cannot set the “Icon Padding” or the “Icon Size” to 0 or a value less than 5. I was inputting a value of 0 rather than using the up/down arrows and that’s the issue. If you set it to anything less than 5, the widget won’t save.
So, if anyone gets stuck again on this, that might be their issue, too. Working fine just don’t try to add your own values I guess!
Thanks!