PS

*rbk - to mix, to stir (HALOT 1179; BDB 916)

Akkadian
rabāku - to decoct (AHw. 933; CAD R 8)
Hebrew
murbäkät - (hop. part.) mixed (BDB 916; HALOT 1179)
Arabic
rbk - to mix, to mingle (Lane 1021)

Attested with both -a- ‘to mix, to mingle’ and -i- ‘to be mixed, mingled’ stem vowels (Lane:1021). Note the meaning shift ‘to be mixed’ > ‘to be confused’ (ibid.)

In Gulf and Yemeni dialects this root is reflected as rbš due to palatalisation *k > š (al-Iryani:341, Qafisheh:251, Behnsted:424, 1386). Forms with k are attested in the dialect of Manāḫa (Behnstedt:1386). 

Mehri
rəbūš - to disturb, interrupt (ML 313)

Borrowed from Arabic.

Jibbali
rɔ̄s̃ - to interrupt, to disturb

Borrowed from Arabic.

Harsusi
rebáš - to disturb (HL 101)

Borrowed from Arabic.