hp28s need repair ?. Autotest fails

[tlfrance]

Hello guys,

I encounter some issues on my HP28S calc. Batteries are new *

1/ On autotest mode, result is : "2 FAIL"
2/ The screen do reset (clear) after i enter more than 2 or 3 lines in the stack
3/ when trying to plot sin(x) for ex, just 2 first dots begin plotting then cacl seems to be freezed. Must interrupt process whith "ON + UP"

Maybe issue can be the RAM chip , but not sure. What do you think about ?

Thanks for help.