I wrongly assumed that the reason these portals weren't working for another player was due to the horrendous ingame lag on that day, as they were working fine for me shortly afterwards. (My sincere apologies to GucciSwag for this mistake.) For some reason, despite these portals working just fine on one character, they failed to work on another despite no lag whatsoever. However, CC-ing solved the problem. EDIT: I've done some more testing, and these seem to be specifically the portals leading off Maple Road: A Split Road - this also includes the portal leading back to Maple Road: Snail Hunting Ground III. It seems that none of the three portals leading out of A Split Road work the first time I try to use them with a character, but they all work after CC-ing and also work on subsequent occasions. EDIT 2: Strangely enough, I've only had this happen on characters above lvl 5. It didn't happen to a lvl 4 I just tried it with. This is what GucciSwag posted on the subject:
It's happened on every character I've made aswell as when it happens I can't open npcs or stores in fm but ccing always fixed it for me
Updating this because a player reported another instance of non-working portal in Maple Island. This time, it was Maple Road: Snail Hunting Ground 1 (Map ID: 40000) and the player was unable to get through the right-hand portal (there isn't a left portal, this is the first map you spawn on). He cc-ed and still couldn't go through. I tried and I couldn't either. And then he mysteriously was able to go through. I, however, had to cc to get through!
This bug has not yet been resolved, to the best of my knowledge. When you enter A Split Road, a tool tip and a non-completable quest pop up simultaneously, and you still do often have to cc or use a potion to get through a portal out of that map.
I knew of this bug before hand and changed channels right after I got the quest. Thing is, it still happened even despite changing channels. There are time that I've gotten lucky and was able to go into the portal leading to South Perry, but the previous attempt that I've done did not produce the same results. The only way I found to fix this was to attempt to go into a portal, channel channels, then attempt to go on again. This works all the time, but it is kind of a hassle to walk from the beginning of the map to the end twice.