Random loss of reverse and neutral, any ideas

so its either reverse and very sluggish drive, or forword gears are fine and no reverse. the trans was rebuilt less than a yr ago, i just pulled the pan n swappedfilter n flushed fluid. there were small metal shavings on the magnet. also changed the aic, and tps. a new kickdown cable was installed although im sure it needs to be adjusted. installed a trans cooler n bypassed the one from radiator (to avoid that check valve inline)

1996 Dodge ram 1500 5.9L 4x4 automatic trans