Warning during geometry optimization via Gaussian

I have some recurrent problem with my DFT calculations [functional: hseh1pbe; basis:6-31+g(d,p), object: porphyrin derivative]. During the MO setting I get:


\*\*\*\* Warning!!: The largest alpha MO coefficient is \*\*\*D+03


\*\*\*\* Warning!!: The smallest alpha delta epsilon is \*\*\*D-01


I did some first-step research over the internet: the only considerable suggestion I found was to decrease the basis since some MOs got linear-dependent. I already decreased it from 6-311++g(d,p) so I assume that it didn't help much. Moreover, simplifying the basis set would mean increase in inaccuracy, right?


Did someone meet and solve this issue before?


