Hi Rangerbazz,
Once the jacks are all the way up or down, you're loading the hydraulic pump motor a bit more than in normal operation. Because of the additional load, it draws additional power. It sounds like you're tripping the 50 amp 12V DC mini circuit breaker through which the power flows. If the breaker repeatedly trips, it may get weaker and start to trip during normal operation.
You might proactively replace the breaker. They're inexpensive and it takes 10-15 minutes to replace. Even if you don't replace it, you should probably get one or two to keep on hand in case the operation gets worse.
You want the auto reset breaker, 50 amp, in-line mounting, like
this one. You may be able to find them locally at an auto parts or marine parts store.
There's a row of these breakers near your battery, probably covered by a red rubber boot. I'm attaching a picture of a typical setup.