4wd problems

Hello, newby here, Please can someone help ? My jimny is a 2008 vvt manual.
The problem occurred suddenly, The car was working perfectly well when I went out to my woods, put it in 4H for about 20 yards up a steep hill then parked up with no apparent issue.
When it comes time to leave I start up, do the 20 yards again (this is on well compacted stone track with no ruts but quite steep) go to change back to 2 wd and nothing. Stuck in 4H and no flashing lights.
I did some reading and decided to get new manual hubs as much to avoid future vacuum issues as to hopefully solve the existing problem.
However I have fitted the Hubs (no Problem) and linked the vacuum pipes with one of the removed hoses.
Now the car is still stuck in 4H and the light is flashing.
I have read that you can fake the vacuum signal for the controller by shorting the wires at the sensor below the battery tray.
What is not clear however is, whether the short has to be momentary as in a quick touch or can you simply leave it shorted for the system to function normally in use? I would like to disconnect the vacuum system completely as it now has no function for the hubs. I know the controller needs to have the correct electrical signals for it to carry out its function to operate the actuator on the T box. Is it really as simple as leaving the 2 wires shorted.
I also realise there may be a fault at the T box but I just want to rule out the vacuum system at this stage.

Transmission wind up. Driving on a grippy surface in 4wd will have cause your transmission to wind up. The electric actuators in the transfer case aren't very powerful so if there is any load on the gears they won't disengage. Normally reversing or turning will release the load on the gears and it will go back into 2wd.
It's nothing to do with the vacuum hubs.

Thanks for the reply, I realise about the wind up issue and I tried reversing etc several times it made no difference. I realise the problem may well be with the actuator and I will come to that but I wanted to deal with a potential problem with the hubs first, that way I can rule them out. They have been slow engaging for some time and the pipes are well rusty.
So the issue now is how do I fake the vacuum ok signal to fool the controller into action.
Before I fitted the manual hubs the he 4X4 light was out but now its flashing, suggesting to me there may still be a vacuum issue (maybe in the valves or pipes) so I just want to eliminate that issue.

As long as you have sealed off the vacuum pipes up near the solenoids then that should be an end to that aspect. Have you examined the wires going into the transfer box for damage, they are quite exposed and relatively vulnerable if you don't have a belly guard. Also the switch is known to fail but that's less common than a wire defect.

I relieved the wind up
Find some deep mud/gravel/snow and spin the wheels
4K revs and drop the clutch like a boy racer :laugh:

Thanks, I have only blanked the pipes down by the wheels so far, next thing was to try up by the valves. Thing is I really wanted to eliminate the valves and the entire vacuum system as they no longer function for the hubs it seems to me to be unnecessary stuff to go wrong and potentially stop the transfer box from working correctly (once I have got that sorted).
If I can fake the required signal then the valves etc are no longer an issue.
As for the Transfer box I did manage a quick look at the wires before the weather stopped me. They all appear intact but soon as I get chance I will get underneath and give all the contacts a good thorough clean.
I know the box is probably all wound up but I don't have soft ground anywhere near me to do it rough style. I was thinking it might be better to take the actuator off and give it a good check over and make sure it at least works off load before I start bashing things around.