Help with building confidence and understanding

Hi yall! I have a lovely mutt who is about to be two who really is a good girl. She is smart, good with dogs and people, a great listener, fantastic hiker off leash. She has a good grasp of basic commands. What I deal with her is that she tends to shut down during training (especially indoors) and doesn’t think it’s “fun”- I have four dogs and she is the only one of the pack who gets very nervous when trying to work with her. All my other dogs seem to get excited and happy to work- even the Siberian husky!

For example, outside on a walk or hike she will go into a down stay with a lot of confidence and good body position. Inside if I ask for the same command, she sinks in on herself and tucks one paw under her body, and does not hold that proper “down” position. No amount of luring or attempts to get her to “untuck” seem to work, if anything it seems like she gets more shut down. She would rather roll over and show you her belly. She’s VERY willing to please typically but when she shuts down mentally like this you can see in her eyes a change.

She does have separation anxiety that we have worked through a lot this year. She is doing much better with crate training, but still seems to struggle at times when I ask her to go to her kennel. I will ask her to go to her kennel and wait while I ready her food and it seems like every day, despite consistently asking for this same behavior of waiting in the kennel twice a day, she will make multiple attempts to break her stay. I did use treats to teach this behavior at first but have weaned off them as it’s been a few months.

Mostly I just want to see her blossom into a more confident version of herself who does not shut down when we are trying to train. I’m wondering if there are additional tasks/commands anyone has had success with helping a dog become more confident. She is a very smart dog and I think encouraging her to work more and have jobs will help. I’d love to grow more as far as my training abilities go too, and I feel like she ended up my dog to push me to be better. Thank you all in advance!