You can configure your display to show Digital Error Count and Noise level to help you see if you have problem to decode the digital data and when you have that problem, only on the control channel or on a voice channel or all of them.
Look at the values, together with the RSSI signal strenght and try different filter settings for that trunked site, also IFX can be used if you enter that frequency in Sentinels profile for IFX. You have to move the system to a favorite list to be able to do the changes without it affecting all other systems.
Note down the values after each change to see if improvements can be made and if one configuration could be the best for your monitoring of that particular site. Try to note down the values for the control channel and for all the different voice channels.