A833 2nd gear engagement issue

Transmission is a 70 model Mopar 4 speed A833 sent to Brewers for rebuild. Unit shifts between all gears fine with motor off but when driving, does not want to engage into second gear. Sometimes it will with a firm hand. Sometimes it will if I short shift to third then to second. Before I pull this thing out and send it back wanted to get some opinions. Any comments would be appreciated.