Similar thing happened to me too. My BTC what I sent to my Waves wallet was in the limbo for a long time, before the transaction went trough. As it turned out I did not set the BTC transaction fee high enough to be a temptation for miners :/.
This is a Bitcoin network problem and has nothing to do with Waves platform. As long as your transaction does not have enough confirmations it will not be credited on your Waves account as WBTC tokens.
I recommend to always check
https://bitcoinfees.21.co before you send a Bitcoin transaction. The site shows what amount of fee you has to add and how long it takes with a particular fee.