Preamble
After a couple years of ownership, and using a keyboard with haptic feedback, the vibration motor decided to pack it in. This happened to my Galaxy S4 almost a decade ago too, but my unfortunate ‘fix’ back then was to replace the device with a Galaxy S5 
Seeing as the vibration motor is located in the bottom module, I thought it to be easily resolved with a replacement part… but none were in stock at the time.
After some digging on the forums here, I came across another thread showing the bottom module disassembled. This was pretty helpful - I used this to disassemble my bottom module, just in-case the issue was loose/dirty contacts, and ended up cleaning the vibration motor connector pads with some contact cleaner.
After cleaning, the vibration worked for a bit… before stopping again.
Repair
After looking around on a few websites for similar looking parts, I finally found a close enough looking replacement on Aliexpress, described as being for the LG G5. I found an identical listing on Ebay and ordered from there instead.
Both motors are shown below - with the old vibration motor on the left, and the replacement on the right. The replacement is a tiny bit smaller than the original FP3 motor.
Here’s a picture I took of these side-by-side with an action camera (apologies for the blurriness) - the size difference is a little clearer here
I don’t have any pictures of the repair itself sadly, but this just involved removing the old vibration motor, peeling the sticky backing off the new one, and placing it in it’s place.
I put a piece of kapton tape over one of the test contact pads in the bottom module, as the metal housing around the new vibration motor protruded a little bit.
The new vibration motor feels very different to the old one - if anything I prefer the original FP3 vibration motor, but this G5 replacement will do just fine.
