Ok. So, I am home for Easter after 8 weeks away at uni. My horse has been kept fit for me while I was away, and I came back ready to get on with our training, aiming for a ODE midway through April. His dressage is looking good, he's working in a double bridle now and it's really letting me ask more of him in a more subtle way.
However, we're having a few little issues in the jumping. He is quite fussy when jumping, and likes to do things his own way without me interfering too much. Therefore, when I'm doing something wrong, he gets very strong and tries to wrest control away from me over fences - and he's fairly sensitive to when I'm doing something wrong (typical TB). It's something that happens occasionally, and I'm glad he does it for when we're out and about, as it's saved my ass a few times, and he's been doing this long enough to know what he's doing and judge his own strides.
Since I've come back this holidays though, it hasn't been an occasional thing. Whenever I put my stirrups up to umping length, even if we're just doing pole work, he races off from underneath me. I can jump him with no stirrups and he's perfect, but for some reason when my stirrups go up I'm doing something weird. I even tried jumping him just in a snaffle one day, to see if I was maybe being too strong with the double, but he was worse (and to be fair, he has quite a soft mouth, so he would have been making a fuss with his head and running out if I was being too strong, and I know I ride him with nice light hands). So it's not that's he's in too strong a bit.
Also, I've been doing cross country jumps out in the woods when hacking, and he jumps them perfectly fine. So what am I doing differently in the school? It's not my jumping position, because if I hold that position whilst cantering round and into the jump, he is perfectly fine. It's something in my seat whilst I'm riding into the jump.
Any suggestions as to what to try to isolate what I'm doing wrong? My instructor first thought it might be my ankles, as they're fairly weak, but when I can do no-stirrup and jumping position jumping with no issues, she's not 100% sure what to do with me. Any suggestions?
(I have no pics/video atm because my lovely horse threw my jacket on the ground and stood on my camera, so not ideal I know, but any suggestions of things to try would be much appreciated!)