Benz Refs stripped screw hole

Just rethread the hole with an appropriate size tap.

Had the same thing with a Dynavector Karat 23R (non-standard size) that I bought used. 
I used slightly larger nylon screws - they're soft enough that they won't do more damage

Benz has a wooden shell but the chassis is threaded aluminium.
Threads are 2.5 mm so perhaps if you try 2.6mm screws might help ?

IIRC, the Benz is a wood body.......

(1)   Make a paste w/ some sawdust + wood glue
(2)   fill in the stripped hole
(3)   when it dries, drill a hole with drill bit that is SLIGHTLY SMALLER DIAMETER THAN SCREW!!

The hole will kindof self-tap when you insert screw for first time.   Should be nice and tight now.

I would explore a longer screw but make sure the thread pattern is the same. A 1/4 inch longer will probably do it.

I did not know it could be repaired.  Thanks.

Using a larger bolt is a recipe for disaster.
Try wrapping some plumbers tape over the bolt - this may be enough to get some purchase on the thread.
Alternately, why not send the cartridge to someone like Soundsmith to effect a proper repair. Should not be a costly repair.   

I would have said use a smaller bolt and a separate nut but having seen the shape of the reference body it looks like there's no way of fixing a nut. Perhaps you could try using the next size up bolt and cutting a new thread? Of course this may destroy the cartridge and risk your headshell as well ... remind me to avoid cartridges that won't take a nut 😏

Go to Home Depot with the current screw and get one 1 size larger....get help from someone to assist you.