Issue with numlock activating when switching screens between excel and software Win10

[nigelog]

For 6 months I have switched between an excel workbook that uses a userform to validate data and another software package that I scan dockets into. Enter docket number in Stratum software finds the job - copy docket number - switch to userform in excel and paste and press enter to validate - switch back to Stratum to enter next number in same column header ONLY now numlock has been activated.
Any ideas where I should start looking??

Only since Windows 10 installed

[nigelog]

downloaded a utility called numlocker - sorted