Deon Derrico is keeping busy in court ... because not only did he file a restraining order against his ex-wife, he's now suing a business partner over a real estate deal.

According to legal docs, obtained by TMZ, the "Doubling Down With the Derricos" star claims a guy named Tyrone Sprewell is attempting to sell a home he says they co-own, before they've fully hammered out and resolved their ownership disputes.

Deon says he's entitled to a 25% stake in the home independent of Tyrone and insists Tyrone needs his sign-off before he can unload the place.

What's more, Deon says he could be irreparably harmed if the house is sold before these issues of ownership are resolved.

Deon is asking the judge to halt any sale of the home for now.

As that mess plays out ... Deon is in the middle of another serious matter after his ex-wife was arrested for allegedly threatening to kill him and their children.

Karen Derrico is currently out on bond ... and her attorney claimed emailed death threats allegedly from her to Deon were actually manufactured by Deon to frame her after a messy split.

We also obtained audio of Karen in a heated phone call with some of her children ... admitting to threatening to kill one of her kids.

The big winners here ... lawyers with billable hours.