Projector color issues

Hello,

I have an Optoma HD20 projector that was working very well until the day before yesterday (I believe the lamp has around 2000 hours). Suddenly, the image turned green and then started jumping from one color to another in a strobe-like effect; I can tell you it’s very unpleasant to watch. I'm calling on your experience to shed light on the cause of the problem and how to resolve it.

I should add that for the past few weeks, I’ve noticed a kind of "posterization" effect on bright scenes in movies, which is less noticeable in darker scenes. By posterization, I mean that the colors that are supposed to be gradated are not; you can see this effect very clearly on the skin of very brightly lit faces, for example.

I’m sure the problem doesn’t come from the computer or the HDMI cable.

Here are images of the phenomenon:

1- normal image:


2 - degraded image:



Thank you in advance for your help!