Delay in switching from eraser tool back to brush tool

Just upgraded to 2018 from 2016 and I immediately noticed a good .5-1 second hang/delay that happens every time I switch from the eraser back to the brush tool. Switching TO the eraser has a very slight delay, but switching back always has a noticeable lag that interrupts my working.

At first I thought this might be because I'm still using custom brushes from Painter 11, but it seems to also do this with Painter 2016 brushes.

This is the sort of issue that makes me consider going right back to 2016 as I really need/like to work quickly, which is disappointing because I was looking forward to playing with the updates in 2018.

So far I've tried this on my desktop and laptop and have noticed this on both, but the specs of my laptop where I feel it the most are:

Win10

Intel i7 Q720 @1.60Ghz

16GB RAM

Geforce GT330M