brake help

I concur with the brake hose(s) as the most likely problem. Crack open the bleeder when the brakes are stuck as suggested & observe the fluid flow. If the brakes release & turn freely close the bleeder & go back up the hose to the fitting where the brake line threads into the hose fitting & crack it open there(after applying the brakes to get them to stick again) & see if they release then. Closely watch the amount of fluid that comes out here. If there isn't a good amount of fluid & the brakes don't release quickly then you have a blockage in the hose(s). If the hoses are old or unknown it's probably best to just replace them anyway. But the procedure mentioned will help isolate the problem if it is the hoses.
Also make sure the pushrod is seated correctly in the master cylinder piston & that the M/C is being allowed to fully return to its rested position. This could also cause a similar problem like yours.
Good luck.