Hard shifting b/t 1&2

[Healey Tree]

Hello. I am new to this forum and new to owning a tractor. My Kubota M5400 (1k hrs) is having trouble shifting from 1st to 2nd and from 2nd to 1st. It is manual 4WD. It grinds - even at a low rpm. Double clutching does not help either. Anything come to mind that an inexperienced operator like myself might not think of?

Thanks so much
Dan