A few months ago i mentioned how I started refilling the carts by leaving them in the printer, this seems to have solved the problem of channels dropping out after refilling cartridges - In the past few months I’ve only had to run 1-2 minor cleaning cycles and not one single dropped channel !
The only annoyance is having to slide a semi rigid plastic strip in between the cartridge chip and the sensor to reset the chips - I use a 1/4 strip of clear plastic I cut from a raspberry container and use some locking tweezers to hold onto the strip. The strip had to be aimed precisely so that it doesn’t deflect into the ridge above the chip but you eventually get the hang of it.
To prevent the ink from overflowing I wrap a strip of paper towel around the syringe tip and against the fill hole. I also removed the stickers from the sides of the cartridges and with my iPhone flashlight on the backside of the cartridges it’s really easy to see how full they are.