Turn by turn sometimes shows wrong arrows

What do you use to create your routes?  If the map data in the route planner you use doesn't match the Garmin map data it can cause issues.  Use OSM maps in your route planner to avoid this.

Also make sure when you are planning your route you don't put any control points directly at junctions as that can cause problems as well as it can cause overshoots.

If the roads you want to use at the crossroads are slightly offset then the Garmin will tell you to turn right (in the pictured scenario) and then left.  If the offset is very small the Garmin often doesn't have enough time to show the second direction prompt.  Hopefully you can see the joggle on the map screen.  Sometimes they zoom in too far at junctions which could make this harder to spot.  The latest firmware has hopefully sorted this but I haven't had enough testing on that to see if has happened.

I've had a similar issue -  wrong turn by turn directions occurring . Routes are planned using Komoot, the first one was

which instead of indicating right at the first roundabout and left at the second the display showed straight on with text underneath saying Second Exit.

Another was

where instead of indicating a left turn indicated a right turn then left at the roundabout.

Beginning to think its not fit for purpose.

If the Garmin turn guidance is turned off, the directions being displayed are the course points text embedded in the downloaded route file. Roundabouts typically use a straight arrow and text description for which exit to take. RWGPS will do the same thing too.

If turn guidance is turned on, you should be getting additional symbols generated by the Garmin which will more accurately indicate turn directions.

Those aren't Garmin screenshots.  Could we see actual screenshots of the Garmin to see the issue?

No they are the Komoot courses it was meant to be following. Did not take a screenshot at the time (how would that be done) but even if PeterK is right about the turn guidance being off the displayed text should have been the third exit not the second. In neither case was there a routing pin at or near those junctions when I plotted the rides which might have caused an issue.

Screen shots can be enabled under Settings>System>Display. Tapping the Power Button takes a screen shot and they are located on your device under \Garmin\Screenshots.

Pinning route controls in or very close to intersections will give unpredictable results.

I just tried a route going through your first example (with York Road) on my 830 and the navigation prompts are correct and the symbols are correct.

The maps are ones I made myself.

Thanks for the screenshot advice. The weird thng re the roundabout one is that Turn Guidance was on - that was the only instance at any roundabout of a text describtion popping up.