Hello,
I tried to play the scenario and it looks fine to me. It updated the mission for me (I had it already subscribed), and the game downloaded a PBO that matches the one that is currently on the Steam Workshop and almost matches the PBO on the Dropbox (there are differences in a few bytes, probably a timestamp and a checksum).

Strange. It still seems to download the mission file when updating the mission, but for me it launches some old version.

In the new mission version onLoadMission text should mention Field Manual, in the old mission file that is now launched load screen mentions Takistan and Chernarus.

I found out why it happens. I changed mission name recently to WLA: Amalgamation. When mission is updated, steam download old [dyn%2fsp]%20whole%20lotta%20altis.altis and WLA%3a%20Amalgamation.Altis folders. It should use the later one, but [dyn%2fsp]%20whole% is loaded and its outdated while WLA%3a%20Amal is updated (unpacked the pbo's to check that in description.ext).

I removed both of those and started the workshop mission again. Now it uses the right folder. Players would need to do that manually currently.

Updated mission again, [dyn%2fsp]%20whole%20lotta%20altis.altis no longer comes back at least (not sure why it showed same date as the other folder earlier). So seems like deleteing it once, fixes the issue.

Did you choose to restart the mission after the update? If there is a save for previous version and one click "continue" the game will use pbo for which the save was made. So until one chooses to restart the mission the game keeps the old version (compatible with the save). Once you choose to restart the mission gets updated. Could this be the case?

No there was first only play-button and later also restart loaded the wrong file.

Found it and fixed it. You could expect it in dev branch very soon (after QA testing). Also found and fixed another annoying bug where saved games were lost if the mission was updated.

Thanks :)

version 1.40.130473