Hello Vandaarc,
We wanted to post here to acknowledge we know of what you speak of. We too have had this exact issue, even though we mainly develop in v1.17. We have an Egyptian development where the player needs to jump across chasms and at times when landing on the other side right near pillars we suddenly find ourselves propelling forward and can't stop moving. Other times we have landed by a crate only to be stuck and at times holding the "c" (crouch) key has allowed us to escape, other times not.
Rolfy had a thread regarding collision modes and, after assisting him with some tests, he managed to produce some findings regarding collisions. I've searched out the thread and the message he posted
here may be of some help to you. The reason I bring this up is because the crate and pillar I would land by had "polygon" collision, and after helping Rolfy and adjusting the collision mode for the entity to "box", the problem was solved.
However, I do experience your same issue on another level. We have a desert level where the player is leaving a city and entering the desert. if the player jumps by the wall that surrounds the city, the same issue of landing and propelling forward happens. It should also be noted that the ground used is a desert prefab environment with sand mounds and hills, not a standard flat segment ground.
The result for us was to:
A) Re-examine the entities we used in proximity to where the player would land when jumping. If possible, change the collision mode on them and if that did not work then move them further from the player's possible "landing point".
B) Since we mod our own source, we have a command we placed in the source that allows us to disable jumping to avoid the issue. In the desert scene, the player does not need to jump, and so that was the only solution we could use to eliminate the issue.
I realize they are workarounds and can be a pain at times, but since we too have experienced your issue, we wanted to give you the info that we collected on the matter.
Twitter: @NFoxMedia
