Error not able to solve after running the model

I am trying to solve a structure where the superstructure is a mix of RCC and steel and the substructure is of RCC, and it is partially resting on a river. So while trying to run the analysis, I am getting the error as  "PROBABLE CAUSE NEGATIVE DIAGONAL =>LDLT MTX".

I tried to apply partial release of MZ and MY, but did not solve my problem.

Also, I am getting an error  "PROBABLE CAUSE SINGULAR-ADDING WEAK SPRING" which I am clueless what to do about it.