Concerns about retention devices after orthodontic treatment

Hello. I am considering a retention device after orthodontic treatment.

It's been about 10 years since I got braces.

Over time, I left the removable orthodontic appliance unused for a long period, so it no longer fits in my mouth.

Slight tooth misalignment is occurring due to neglect of the retention device.

The retention is maintained somewhat with a fixed retainer on the back of the teeth, but the molars are not fixed and gradually rotate.

Is it better to create a new removable retention device?