6 year old pooped herself

My 6 year old daughter out of nowhere has started pooping herself.. it’s now been 3 times with in the last month maybe 2 weeks that we (her dad & I) noticed she popped herself. It doesn’t look like she just simply forgot to wipe or didn’t wipe right, because she’s done that before where she doesn’t wipe right & theres a bit on her underwear. This time there’s ALOT like a big thick chunk & it’s all in her underwear. When asked the first time she admitted she just didn’t make it to the bathroom so we just said “okay that’s okay just make sure to pay attention to your body and go when you need to go so this doesn’t happen again” we left it at that because we get it accidents happen. Second time again & now third time again she said she didn’t make it but this third time she tried hiding it. I’ve shown her how to properly wipe herself & how to do it & we’ve practiced many times how to wipe. And she’s always been very good at going to the bathroom when she needs to go. She’s never done this before other than the occasional streaks in her underwear which is understandable we’re just completely confused as to why this is happening all of a sudden…