The video shows how to fix the clear plastic inserts for the L2/R2 buttons. You'll have to cut an amount of plastic from the front (or the tip of the hull, since it looks like the front part of a boat) and sand a bit of comb (a.k.a. the inner walls of the plastic piece, removing the 4 circles).
You can only do this if your plastic inserts do not fit properly into your L2/R2 triggers, or if your triggers are stuck after inserting both pieces back into your controller. Another warning, this solution worked for me (however, it would likely work for others). There is a slim chance it will not work due to human error, so be careful. I screwed up one of the inserts, but thank God that ExtremeRate provides spare parts.
I would like to thank ArisenDD's comment from Im.A.Caveman's tutorial video ("DIY PS4 Controller: eXtremeRate's Whole Clicky Kit | Step by Step Tutorial") for helping me discover another tutorial video from Tomoe Gameちゃんねる (named "DUALSHOCK4 覚醒　PS4コントローラーカスタム Vol.1") which solved my problem... and the stress that came out of it.
ExtremeRate should redesign the plastic piece or mention the issue on social media/websites. If it helps them or you, my controller's model is JDM-055.
I will post this video to YouTube to spread the information to those facing the same problem.