Ivan Vegvary writes:

Advice appreciated.

You misunderstand the process.

You have to vent the receiving tank.

You have to invert the tanks such that liquid is being fed into the
adapter.

You have to waste (by venting) a lot of flammable gas to overcome the
thermodynamic work needed to move the stuff from one place to another.

I used to have a refillable propane bottle that had a vent you opened with
a wrench. Worked great.

You can completely refill disposable bottles if you can get the vent to
work.