Where did I go wrong with my brisket?

Hoping for some insight here

I have a RecTeq 590 pellet smoker and have had really great success with ribs and chicken, but I just can't seem to figure out where I'm going wrong with briskets.

Tried my 4th attempt at a brisket yesterday. Typically comes out a little tougher than I hoped for, but I think it's because I was f pulling too early.

So this time, I swore I wouldn't mess with it, and check for tenderness before pulling.

Set the smoker to 250°, 9 lb brisket, placed it fat side down, set a water bowl, and some spritzing with apple juice every hour until the bark looked good, which was about 170°. Pulled it in to wrap, gave it some hefty spoonfuls of tallow, and threw it back on with the smoker now at 275°

Probed the flat at 190, and was still pretty tough, so I let it go to 195° Still tough, so I let to go to 203° A little better, but still not butter tender Probed at 210° and again, better but still not butter.

I didn't want to ruin it completely, so I ended up pulling, and sitting in a cooler for a little over 3 hours.

It didn't come out bad by any means, wife and I still very much enjoyed it, but I'm chasing that super floppy super juicy goodness that I just can't seem to get right.

Few photos we took: https://imgur.com/a/HICmRAq

Hoping for some tips or insight here as to what else I can try next to improve

Thanks in advance and happy 4th all