Osc appeared on the right-hand corner in my DMA 4500

i have two problems the first one:after power on,the DMA 4500 begin self-check and while doing self check,sudanly the display became pink and the instrument return to the begining again.some tims after the self-check finished,the display became pink and return to the begining.

the second problem:-Osc- appeared on the right-hand corner and the condition will not change to valid even after reached to the requred temparature.i need ur help to resolve these problems