Welcome,
This is normal for a very small vocabulary with words with few syllables – it’s been discussed many times here and elsewhere so you can probably get some good suggestions by looking back through previous discussions. You may wish to investigate either using a grammar, which this blog post should give you some information about:
https://www.politepix.com/2014/04/10/openears-1-7-introducing-dynamic-grammar-generation/
But in that case you will need to have more than two words in your grammar or it won’t help with this issue, or you can also give Rejecto a try since it is designed to reduce this issue when using language models: