I tried all the possible options in random.method, but I still got the same message -

Error in solve.default(vcov(x)[names.coefs_wo_int, names.coefs_wo_int],  : 
system is computationally singular: reciprocal condition number = 9.29205e-18

The reciprocal condition number changes for the different options.

However, when I log transformed one of the variables, the issue didn't occur.

I tried all the possible options in random.method, but I still got the same message -

Error in solve.default(vcov(x)[names.coefs_wo_int, names.coefs_wo_int],  : 
system is computationally singular: reciprocal condition number = 9.29205e-18

The reciprocal condition number changes for the different options.

However, when I log transformed one of the variables, the issue didn't occur.

Edited: Aug 20, 2022 - I think this is because of degrees of freedom issues and also STATA can model such a case but R's current package is unable to.