DMLfit.MultiFactor raises: system is computationally singular

[yotamroshuji]

Hi,
While using DSS's DMLfit.MultiFactor with a complex design, there are many times where I run into the following error:

Error in solve.default(XTVinv %*% X) : 
system is computationally singular: reciprocal condition number = 3.45232e-20
Calls: DMLfit.multiFactor ... DMLfit.multiFactor.engine -> DMLfit.oneCG -> solve -> solve.default

I get a similar error (computational singularity) in a few different experiments, for example:

• 144 samples, from 7 major cell types and 28 sub-celltypes, with around 125,000 CpGs.
• The formula I used is: ~celltype+major_celltype, and I made sure that each group has at least 3 samples.

Are there any ways to handle this error, or at least workarounds for it?
Thank you, and I appreciate the work done on DSS very much!