Randomly disappearing Tender button in POS?

Hello All,Relatively new to POS, but have a question (more a confirmation) for the community...

The scenario is simple, I am adding a new Tender Option (could have been anything else, but I will stick to the specific case at hand) and have made some modifications across the code to accommodate the proper logic and handling... By the way, please disregard the lack of customization standards not mentioned in the text below... The example is explained as if it were base product modifications just for ease of reference. 

One strange thing that occurs on our POS Clients is that very randomly (without a specific reproducible pattern) the new Tender button added simply does not show. Majority of the times it does, but after the first time it isn't shown it will never show again unless the Client is restarted....