Puzzled why this thing needs a cell/battery carrier which just adds a load of complexity and potential problems for a basic parallel cell arrangement.
Many more contact surfaces in the current path, and bits to go wrong, in design, manufacture/assembly, and in service. Added cost, mass and volume too.
And complication when changing cells.
Edit: Trying to tug them out, perhaps with some fabric ribbons to help, if you remembered to tuck them behind when loading, or bash them out, or insert fingernails, penknife etc and damage the wrapper. Whilst tugging the springs sideways and further compromising their weak performance. If a plastic spacer put at the button end to prevent reverse polarity, even more difficult.
Edit2: If suffering poor performance and suspecting excessive resistance in the current path, well, there are so many places to suspect, look at, and try to fettle, good luck trying. Unless it’s just a hobby to muck about with.
Instead of faffing about with a carrier, just unscrew, drop out old cells, drop in new. run a finger around the top to check they are all the correct way up. Close.
The simple SRK/Q8 etc. arrangement is tried and tested. It also suffers bump disconnection because the contact ring in the head is solid, not spring loaded. But that is easily avoided with suitable circuit design.