Struggeling with raw mats

Dear Commanders,
Today i started a trip to fill up all my raw materials so that i can finally engineer my python mk2 and others from half assed grade 3 to grade 5 to really rip apart the NPCs in Operations.
Now i followed this video as far as i could: https://www.youtube.com/watch?v=VItBzHOsJSo

I have an equipped Caspian with everything i need, and have arrived at HR 3230 3AA to start farming selenium and if possible technetium.
Now i somehow found some Braintree's after surface scanning but they do not show up as contacts from my Caspian. I tried going on foot with my scarab and then i could selesct them, detach and gather. Just that i hoped to do it a lot quicker with the limpets.
So when i shoot the brain trees with the flak, then go away to get out of render distance and deploy my limpets (while not seing any contacts of materials) they do go get them, but only very slowly and very few. Sometimes they just deactivate, they dont destroy themselves, they deactivate.

What am i missing, there has to be something that i am doing wrong right?
Any Help would be greatly appreciated!

I not really new to the game but just started engineering and after only gathering a few for a while i want to fill all up to have a break from constantly running for additional mats.

Additionally: How do i get my Scarab back into the caspian without reloging?
when i get under the ship it doesnt let me put it back in, i can only enter the
ship via foot somehow.

If you have any tips on anything engineering related please tell me!

o7 CMDR