The way sneak attack is supposed to work is that you must either have advantage on the attack roll (that is, the roll you are making is an advantage roll; the factors that go into this are irrelevant), or else you need a creature hostile to your target (usually and ally of yours, but not necessarily) that is within melee range and is not itself incapacitated, and you must not have disadvantage on the roll (that is, you must not be rolling two dice and taking the lower - the factors that go into this are irrelevant).
This means that if you have disadvantage coming from five sources, and advantage coming from one source, as well as an ally in melee range of your target then Yes you can use and apply your sneak attack, because the Roll you are making is not at disadvantage - it is a flat, normal roll.
Up until the last time I checked, this was not working correctly in BG3 - and that any source of disadvantage, regardless of whether your actual roll was at disadvantage or not, was knocking out your sneak attack, when it should not have been - this has always been the case in BG3, but was not as visible because up until patch 6 (I believe), it still let you use the sneak attack button - it just didn't apply it if it didn't think the conditions were satisfied. As of patch 6, however, sneak attack was made to give an error and lock out instead, when it though the conditions weren't met, and this made the mistake in the coding far more visible to far more players.
At most recent checks, this was still being a problem and sneak attack was not allowing itself to be used in many circumstances when it should rightly be satisfied; if this has been truly fixed, then that's good to hear.
This does not negate the fact that sneak attack is still drastically reduced in its flexibility and availability in BG3 compared to the 5e system which Larian have sold this game on being a landmark representation of; we need to be able to apply our sneak attack to any suitable attack roll, once per turn - including on opportunity attacks on other creature's turns.