I use rechargeable interchangeable batteries wherever I can, but I recently ran into some issues with an ultra-cheap BDC “massage” pillow. The OCP in the batteries was getting triggered and the motor would stop and start spinning for 10 seconds at a time. Tried to add small value resistors and capacitors to it but nothing worked and I had to get a pack of alkaline. Only now do I remember I have a bunch of spare 18650s and USB battery charging boards that I could’ve retrofitted!