Have you been to see a physio? It would be great to find out what's causing it but ultimately it's more important to find out the what you can do about it and your best bet there is an experienced physiotherapist.
see my comment from Nov 4. 9-10h/week is not slowing down. Get to the gym and do some cross training before it gets worse.
Thanks, I should probably look into finding a physio. Well I mean, no number was specifically stated. I will start doing that though, I am still allowed to do interval sessions?
DD, Find a physio and ask them that question. They will be able to assess the injury and let you know what will aggravate the injury and what won't.
Until then, if something is causing it to hurt, stop and don't do it. Take at least 2 full days away from that activity before trying it again. I would guess that you should take at least a full week with absolutely no running or orienteering). Do cycling and water running as cross training and do of calf stretching (say 3x40 seconds per leg straight knee and 3x40 seconds bent knee multiple times per day). That would be a good start. The number one thing for you right now needs to be preventing this from getting worse. This is the injury that stopped me from orienteering back in 2015-2016 and the injury is still bugging me. A month off of running if that is what it takes is better than 4+ years off :/
Just pointed out you didn't take my advice...:-)