She was having trouble holding her weaves for 3 reasons, iirc:
1 - she was getting very tired from channeling so much
2 - she had never un-woven something before
3 - all the channeling was messed up because of the Bowl being used to far greater effect than intended. Everyone's weaves were messed up around Ebou Dar for a while (e.g., Rand fighting the Seanchan). This is probably the most important/singular reasons for the weaves' slipperiness.