The 8 squelch will probably receive signals too noisy to be decoded and will hesitate on that CC too long until it will continue to scan.
First check that you can successfully decode the signal while entering the voice channel manually to monitor it stationary. If that works you can then adjust parameters for scanning.
The dwell time depend on how many control channels you have in the system. I would recommend 0.3 sec per CC that you can hear at one time. If you hear 3 CC then use 1 sec, if you hear 6 CC then use 2 sec.
If the system doesn't use, or rarely use, the slot 2 on the CC I recommend that you remove the CC frequencies. TRX uses dwell time per system, not per site as 536, so it depends on how many simultaneous carriers with DMR signalling you scan and how many TGs you lock out. If you monitor all TGs then the default 1 sec will be more than sufficient. If you lock out a lot of TGs and only monitor a couple, then you need to calculate how many simultaneous active voice channels you can receive and multiply with 0.3 sec and if the system often gets fully loaded with voice traffic then you also need to have the CC channels in scan and must also consider 0.3 sec per CC.
For testing purposes you can easily try a 5 sec dwell time just to be sure that you do not have a dwell problem. But as I have mentioned, check that you can monitor the voice channel manually that the 536 uses when you do not get anything when the TRX are scanning.
/Ubbe