Sure you haven’t accidently returned to the default routing of the Tascam software mixer?
For example, the default RME driver/mixer installation routes all tracks to the phones output, in addition to the expected 1->1, 2->2, etc, thereby interfering with using Cubase’s Control Room. I had to un-route those extra phones sources so I only heard Cubase’s Phones output through them.
As enjneer wrote, check your monitoring routing matrix for unwanted connections. It may be as simple as a single recording mode switch changing routing matrices.