Loader Loader won't work after using rear hydraulics

[turboviking]

Hello! My 4610 works awesome in most respects, but lately I have been doing a lot of work with the box scraper and when I press the electric switch to change back to front hydraulics the bucket will tilt but the boom won't raise or lower. Just makes the engine grunt. If I continue trying it is fruitless. If I turn off the engine for about 30 seconds, it corrects itself - as though there is hyd pressure building up and shutting off releases it.

Any ideas? I have all optional rear hyd - 2 cyls and a passthrough . Any ideas? Thanks, as always, - Troy