There is a bug fix out for Fedora that fixes what looks like a similar issue for V2.99.917-9 (https://bugzilla.redhat.com/show_bug.cgi?id=1226531). Apparently DRI3 (which was enabled on 917-2) was disabled in 917-9. It would be nice to have a later version available in Debian to test out DRI3 and whether this bug is fixed.