I would do two things --
1) When you bring the slide in, make sure you hold the retract switch for 3 seconds before you release, (per HWH recommendations) to make sure the pressure builds up to hold the slide in.
2)If that doesn't work, look at replacing your slide retract/extend solenoids. They replace quickly; my HWH tech replaced both in about 20 minutes.
Either you haven't built up pressure to hold the slide in, or your solenoids are leaking pressure and allowing the slide movement.
That's my 2 cents worth.
2019 Winnebago 22M
2015 Jeep JK Rubicon
Former Owner, 2006 Alpine Coach 36MDDS
Former Owner, 2005 Tioga 31M and Arctic Fox 22GQ