As I read this again, I realize that you have two distinct problems:
1. The LOS from 6b aa18 to t11 (I think you actually meant Y11 which would have a bridge in it according to your image). The LOS engine is drawing the LOS to the -1 level of the water and not to the bridge. This is a bug and I will note it (can't promise an early fix). Thanks for passing it on.
2. You got an EEK a bug when you drew a LOS check from Offboard to 6aJ10 (as shown in the last chat entry in your image). The error is because the starting point is off the map. We are trying to trap all these errors in VASL and simply bounce you out of the LOS check. The effect for a player would be that nothing would happen visually, no LOS line would show and, more importantly, no EEK a bug. This should mostly be fixed by 6.4.0 but I have found one or two special cases that still triggered the bug. Those will be cleaned up in future versions. It is easy to unintentionally draw a los check from/to an offboard point, especially in a hex with its center point on a board edge.