I think the one I had trouble with was a 395.
https://www.electro-tech-online.com/custompdfs/2012/09/dremel_moto-tool.pdf The issues are:
1) The bearing support - There really isn't any
2) The way the parts "drop into place" is designed very poorly. The electrical connections are not firm at all. Thus, anything that might compromise the connection such as starting and stopping or a loose connection will eventually kill the triac.
3) The speed control was a bit wimpy too. They did use a deposited resistor, but the slider isn't designed to last. HP X-Y recorder sliders were really designed well.
It seems like in the UK, you can get parts, but not in the US.
I already had a kit and lots of attachments and I had to buy them over again when all I wanted was the 4000 rotary tool. I had no reason to take the 4000 apart, but it wasn't worth me getting the Dremel repaired for free either. I had to have the Dremel ASAP and could not wait for a repair, so I had to buy the 4000.
There are lots of articles that show when drilling PCB boards shows that the Dremel has problems with runnout. It's not designed for precision in mind. One recommended replacement is Proxxon.
I also already had a storage case. I think I'm using one of these:
**broken link removed**
The same guys that design the storage cases design packaging. You can't add stuff.
I have a Dewalt angle grinder where the rubber strain relief on the cord next to the body has to be bent everytime you put it into the case. It's very difficult to add blades or even a wrench into the case. I use it primarily for an unconventional purpose, the grass in the cracks in the sidewalk.
After I kill the grass I use something like this brush:
**broken link removed** to remove the dead grass from the crack.
In an aside, I got a Dewalt DWD460 drill **broken link removed** for a song like $150 and I use it to drill 2" holes in the ground. It should also work well when using those 4' long flex drill bits A battery powdered 3/8" VSR works most of the time. I have a Bosch Demolition hammer, but it doesn't have a drill mode. It's great for digging in the ground with a spade. I got this
http://www.toolup.com/bosch_11316evs_sds-max-demolition-hammer.aspx for a good price. I rebuilt it for $100 and it needed a few parts that were not in the standard kit. It's a useful too though.