Need help with Razer mouse middle button issues

I have a Razer Deathadder Essential that I got a couple of years back. Its in pretty good shape aside from my middle mouse button, which has been experiencing issues of late.

I primarily use it to play Dota and work on Blender, both of which largely require my middle mouse button. Both scrolling and clicking seem to be a bit jittery.

The scroll is functional but it registers reverse scrolls randomly. The click sometimes works and sometimes doesn't. This messes with any functionality I need especially in Dota which relies on quick clicks. As for Blender, I just use my drawing tablet but I can't use it for too long because my hands start to cramp holding a pen.

I've tried opening it to see if some simple cleaning would fix it, but nothing seems to obstruct the nubbin that registers the click. The problem still persists after cleaning. I did however notice that the nubbin moves a bit every time I scroll the wheel. I don't know if that is a problem or not but I felt it was worth mentioning.

For anyone wondering why I haven't taken it to a service centre yet, I'm from India where Razer support is practically non-existent (courtesy of friends who are also Razer users). Which is why I'm here asking for any help. I'm willing to try any method to fix it since it is a really good mouse that I got for relatively cheap too, and I'm not exactly willing to replace it yet.

Thanks for any help you guys are willing to offer. This seems to be my only resort lol.