Read this, the sentry is there for far more important reasons than protecting the clutch packs. As much a safety issue as an operational issue.
The system is designed to be shifted under load. If all is functioning properly there is a slight overlap where the off going clutch still has some pressure in it's circuit while the on coming clutch is started to apply. This is why there is a bit of delay between moving the shift lever and the actual shift taking place. With the "test harness" in pace it just bangs the pressure to the on coming clutch even if the pressure to the off going clutch hasn't decayed.
the main things to do to increase reliability is to rewire the sentry supply power as outlined in service bulletin S-4841 option 2, and to rework the sentry ground especially if it is one of the units where the sentry ground was incorporated in a relay mounted in the lower right corner of the electrical compartment. Adjusting the regulated pressure to 270-290 psi will also help the system function better.