Haven't had any issues since the new firmware update the other day. If anything, wifi seems improved. Have you tried rebooting or even refreshing device?
Possibly you go go into device manager and find that Marvell adapter, I believe. Then just roll back the driver to previous one. Then your wifi should be good again if other methods don't work. Good luck. Not sure what it is. I have 128gb model and update went smoothly for me.