For COME, practically all Berber languages consistently use reflexes of the proto-Berber word *asəʔ. In the largest Berber variety, however - Tashelhiyt, in southern Morocco - this root has been lost, and a quite different verb is used: ašk (ⴰⵛⴽ). The original meaning of this verb can still be seen in other Berber languages, such as Tamasheq: GET LOST (a meaning which in Tashelhiyt has been replaced by what's probably a borrowing from Arabic جلا.) Presumably, GET LOST came to mean WANDER, and WANDER (over) came to mean COME.
In Songhay, GET LOST is *dere(y), preserved as such in most varieties. In Korandje in western Algeria, however - uniquely within the family - this root's reflex has undergone a very similar shift in meaning: dri now means GO. (Songhay speakers might assume this comes from dira WALK, but this word, from Proto-Songhay *dida, rather corresponds to Korandje zda WALK.) Meanwhile, Berber *aškəʔ GET LOST has itself been borrowed - probably from Tamasheq - as wuška GET LOST (the vowels reflect the Berber perfective form.)
Both changes can be summarized as GET LOST > BASIC-MOTION-VERB. Lexically, Korandje shows heavy influence from southern Moroccan Berber, much of which seems to match Tashelhiyt better than it does the Southern Tamazight varieties currently spoken closest to Tabelbala. That makes it rather tempting to seek a contact explanation. But if Korandje was copying a Tashelhiyt pattern, why would it replace GO rather than COME?
To make sense of what happened, I think we have to envision an intermediate earlier stage where WANDER (from GET LOST) was getting used as a generic verb of motion irrespective of direction in some (perhaps expressive) contexts. Both Tashelhiyt and Korandje require direction towards (and sometimes away from) the speaker to be expressed with a directional morpheme outside the verb root proper, so no ambiguity would necessarily result. From this situation, WANDER could end up replacing either COME or GO, while still maintaining the existing (seemingly superfluous) lexical distinction between the two by keeping the other root.
Now I think about it, British English offers a possible parallel for the initial stages of such a development, with particles substituting for the directionals of Berber and Songhay. In phrases like "he wandered over" ("he came over"), "he wandered off" ("he went away"), the original implication of aimlessness has faded away in informal usage to the point of being virtually absent. Should we expect some peripheral English dialect to replace "come" or "go" with "wander" altogether? Check back in a few centuries to find out...