I sell these at my work, LEDs are indestructable, if there is a problem its the controller or transformer

Hello!

I have waterproof LED light strips behind my desk and for some reason. The on, working part is the colour I want (Red). Part of it is locked blue, and the rest is very dim red.

Where the small strip of locked blue is, the inside looks like it has condensation, or is frosted. I have got it to work again after tapping it a bit, (On a small block like part of it with 3 wires coming out.)

So I was wondering:

How can I fix this

How can I prevent this

What caused it?

Thank you!