Just upgraded to Mojave and all my macros with clipboard Paste actions stopped working. My workaround was to insert a 0.25 second pause in front of each Paste action. Not a question - just sharing.
There are no other reports of anything like that, so I think there is probably something going on on your Mac.
A lot of people have had accessibility issues until they toggled the accessibility checkboxes, but a Pause presumably would not resolve that.