I monitored the Xorg logs with tail, but during and after the freeze nothing was written to it. I also checked the log of the xsession and the only new log entries I got were these:
qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 39036, resource id: 123732553, major code: 15 (QueryTree), minor code: 0
qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 41492, resource id: 25988548, major code: 3 (GetWindowAttributes), minor code: 0
qt.qpa.xcb: QXcbConnection: XCB error: 9 (BadDrawable), sequence: 41493, resource id: 25988548, major code: 14 (GetGeometry), minor code: 0
qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 50009, resource id: 136315091, major code: 18 (ChangeProperty), minor code: 0
qt.qpa.xcb: QXcbConnection: XCB error: 3 (BadWindow), sequence: 50125, resource id: 44045666, major code: 18 (ChangeProperty), minor code: 0