Following preparation with: Salicylic Acid 1%, lactic acid 10%, urea 10% in lipophilic Creme ad 300 g, gives problems.

Sorbitansesquioleate is an ester of sorbitan and oiieic acid. The water phase of your cream is quite acidic due to the presence of a large amount of lactic acid so that it is not excluded that the W/O emulsifier is slowly hydrolyzing. Degradation products have no more emulgatorical properties.  

There are two solutions

1. You prepare AVA yourself with 5 g less water, which you replace with 5 G cetyl-  or cetostearyl alcohol.

2. For lipophilic cream make use of Unguentum cetylitic   Aqua

Per 100 g is the composition cetyl alcohol 2.8 g; wool grease 7 g; Vaseline 60.2 G and water 30 g