My experience with this is all about the impeller shaft.
The impeller shaft WILL wear out over time. It's a user-replaceable part. You can buy a new one for a few dollars online. Grab the one that's in there with a pair of plyers and pull it out. Put the new one in the hole on the bottom of the open cavity. Push the impeller shaft against a hard surface and you'll feel it slide it.
Then I use a bit of food-safe synthetic lubricant on the shaft.
I replace my shafts once a year and have never had one not start after a power outage.
Before I started doing this, I would frequently have them not start up. When I checked the shafts on those they were worn and rusted.
Here are some pictures of my worn impeller shafts:
I have quite the collection of Aquaclear
HOB filters, and I have pointed out on various forums that the impeller shaft is removable and needs to be replaced occasionally, as it wears out and rusts. The impellers, on average, cost around $10.00, and I replace them once a year.
Tonight I was putting away an Aquaclear 30 for long-term storage,and I pulled the impeller shaft out, and is was worn and rusty. So, I'm going to replace it before I put the filter away.
Looking at other
power filters that I own or have owned, the impeller shaft is usually part of the impeller. So, to replace the...
And here is a reddit thread about an AC110 impeller shaft wearing out: