It is hard to offer much in the way of concrete advice without a working example that shows the problem. Please see How do I post a question effectively? and edit your post accordingly.

Until such time, all I can do is take a guess (although a somewhat educated one) that perhaps, somewhere along the line, your process (or one of its threads) managed to send a Linux terminal escape code to change the terminal mode, as for example do some curses applications.

One way you can get down to the raw bytes is through the use of the common script(1) utility. Run your program under that, and then look at the typescript file with a hex editor to spot any unwanted control codes.

Please do consider coming up with a minimal example that illustrates your problem, and consult the above links for possible diagnostic help.