I have a solution, I use it all the time, same results.  Feel free to tip me with a free play Nitro!

Instead of typing in the bet, go to a notepad, or something on your phone, and type whateber your bet is, and then copy paste it.  Then, go to the betslip, and paste the bet in, instead of typing it.  Works everytime.  On Android, you long press the blank bet area, until the "paste" button pops up, then it'll paste as is.