Just did some more tests to see if the occasional stutter (once every 20-30 minutes on the laptop) changes any:

1 - Moved the Steinberg UR22MKii from a 3.0 USB port to a 2.0 USB port (I'm not using any USB hubs at all).............still stutters the same.
2 - Changed the audio/MIDI setup to use onboard ForteDXI soft synth for both audio and MIDI thru internal Realtek HD Audio board via ASIOFORALL Driver.........still stutters the same. This configuration is actually worse because of the extra processing load the soft synth puts on the laptop (more noise and pops in addition to the stutter).

The normal laptop configuration is the UR22MKii (with latest firmware upgrade) into a USB 3.0 port, using Steinberg's latest ASIO driver for the UR22MKii, with a Roland SC88 hardware synth connected to the MIDI out of UR22MKii, with SC88 mixing UR22MKii audio output with SC88's built-in line mixer, combined output going to powered speakers. Works great except for stutter once every 20-30 minutes.

I also have a Windows 10 Fall Creator desktop loaded with Build 512 of BIAB. That is set up using the ForteDXI soft synth with the ASIOFORALL Driver, routing both audio and MIDI from the synth directly to the onboard Realtek HD Audio board in the desktop. Works perfectly, no audio stutters after at least 1 hour of running the Jukebox player. FYI, I couldn't get the WAS driver to work properly on the desktop after loading Build 512 (tremendous latency problems....I reported this to PG). On this machine, 512 works OK with MME or the ASIOFORALL Driver however.

I still think the laptop is suffering from some sort of Windows 10 related memory management issues, or possibly data loss via the USB interface. Hard to figure out what's going on. Maybe I should put a set of wheels on the desktop system and use that for the portable system!