yeah id remove the sump, take the caps off the rods and check them out, see if its more than 1 failing, if you cant find anything wrong there then remove the main caps 1 at a time and check the bearings there too, refit it before removing the next one.
if you find a failed bearing you need to try determine what caused it, might need to measure the crank to see if its the correct size for the bearing used.
talk to your machinist that machined the engine for rebuild to see what they think caused it.
if nothing is found get some new bearings, what brand did you use? maybe try a different brand.
i wouldnt drive it anymore or the cost of a new gasket for the sump and some big end bearings might turn into and new crank