|Without your code (and probably your data)?
We have no idea why this happens - there are just too many different things you could be doing! There is nowhere near enough information here for us to begin to help you - we have no idea what you are trying to do, or where you are starting from.
Start here: Asking questions is a skill[^] and think about what you need to know, and what you need to tell us in order to get help.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
"Common sense is so rare these days, it should be classified as a super power" - Random T-shirt
AntiTwitter: @DalekDave is now a follower!