Deepspeech training

I trained on some other 64k audio sets and exported the model and result was quite good then I trained on 600 audio sets from the same checkpoint and again exported the model. The problem which I am facing now is it does give inference perfectly of words in 600 audio but not doesn’t give any correct inference when words said from the 64k audio. Instead the result i was expecting was in total it will give me inference of both 64k and 600 audios but it is only giving inference of word said from 600.