Lower unit

[Big tiny]

I’m having problems after a long 6hr ride to go fishing I backed my boat in the river and it wouldn’t go in reverse. After driving it down the river a bit ,it would go in reverse. The next morning it wouldn’t go in reverse until I rode it for while then it went in fine. I don’t know what this sounds like so I checked the gear case oil and this is what it looks like y’all tell me what ya’ll think. Is this amount of metal shavings normal.