TV Server can get mixed up when changing between channels with the same SID and PMT PID. This situation can be quite common with ATSC channels as the ATSC scheme has a structured organisation of channels on muxes:

ch 1: SID = 1, PMT PID = 30
ch 2: SID = 2, PMT PID = 40
etc.

h4. Steps to Reproduce
1. Start watching channel 1 with SID x and PMT PID y.
2. Attempt to change to channel 2 with SID x and PMT PID y.
3. If the PMT callback from TsWriter is triggered [for channel 1] between when the PMT callback is set up for channel 2 and when TV Server waits for PMT to arrive then TV Server will hang perpetually.