Just encountered this problem myself, it was driving me crazy, until I disabled HW acceleration, which made it go away. I have never noticed this before (though I've been mostly using the mobile version recently.) Been a Spotify user since the invitation-days.
Spotify version 184.108.40.2061.gdb77255f
OS: Windows 10 Education 1903
CPU: Intel Core i9-9900K
RAM: 32 GB 3200MHz DDR4
GPU: Nvidia RTX 2070
Windows and Spotify are installed on a Samsung EVO 960 m.2 SSD
I have the same issue on my laptop. My spotify is lagging really much on full screen. Turning off hardware acceleration helped but it still didn't fix the problem. It still keeps lagging. I tried reinstalling it but that didn't help. At the moment I prefer the spotify web player because it bothers me so much.
Im on version: 220.127.116.115.g566c8beb (Microsoft Store-version)