Investors in a $120 million historic hotel restoration project in Texas say the project manager is unlawfully soliciting additional capital that would make it hard for them to recover their investment.

The Baker Hotel legacy investors say an attempt from Thomas Randall Nix to raise up to $30 million is prohibited because there are two vacancies on the four-member board that he refuses to fill, according to a lawsuit filed Monday in the Texas Business Court.

Nix, the investors say, wants to merge the investment partnership with a shell company he owns. The move would push them to the end …