Prediction adds the number 6 (six) to many words. Across two phones.

Has anyone had an issue of the left prediction bar showing a correctly spelled word, but with a 6 added to the end of it?  It has happened to me for almost a year and I finally got fed up and decided to ask. It started on my previous HTC and has carried over to my S7.  I tell it to forget the words often, but it just keeps happening.  At least a couple times a day.  It's always a "6", never any other number.