When placing a double angle bolted-bolted connection with two beams that share bolts across a column web – the connection seems to be calculating the distance from angle back to center of slot on the side of the larger beam web and using that value for both sides of the connection. This makes one set of holes have a center-center distance that is not equal to the other side (please see attached picture).
This is only an issue when you're using slotted holes in the connection - for standard holes, the connection locates the holes correctly. When using two beams of different web thicknesses, this can create enough of a difference in hole location to create a physical clash and make the connection not.