Tvheadend

If I start a recording (on any channel), everything looks good. At some point (I can't see any pattern to when it happens), I start seeing constant continuity errors for several minutes at a time. Then, all of a sudden, they disappear and everything returns to normal.

My setup:
Host:
Ubuntu 18.04 LTS (latest updates)
BlackGold BGT3630 (DVB-S2 tuner)
AMD Ryzen 7 1700
Asus PRIME X370-PRO
16 GiB ECC RAM @ 3000 MHz (14-17-17-36)
KVM/QEMU VM:
Ubuntu 16.04 LTS (latest updates)
Tvheadend 4.3-1362~gbaf1f92 (latest) running on the VM
Latest BGT drivers from here: http://git.cblinux.co.uk:5010/Blackgold/BGT3xxx-fork-for-cxd2837

I've attached the debug log from Tvheadend from the VM. You can see a boatload of continuity errors suddenly start on line 12599 (timecode 16:02:57.315) and suddenly end on line 206011 (timecode 16:11:57.060). I've had a look in dmesg and journalctl on both the host and VM and cannot see anything that coincides with when the errors occur. In fact the VM logs show absolutely nothing that isn't from Tvheadend (since that's all the VM is running). "Idle scan" and "power save" are disabled in Configuration -> TV Adapters.

Does anyone have any ideas about how to debug this? Has anyone seen something similar themselves? It's definitely not the satellite or cables because I have never seen this on my old Windows server running MediaPortal (which is still running in parallel with a BGT3600 because of this issue).

Thanks for any help.