Definitely some issues with the sending process. Tried sending 100,000 out of a balance of 212,000 and it says insufficient funds after cutting it up into 25 transactions. Right now seems like sending multiple small chunks manually is working far better than large lump sums.
Noted, thank you. You could try stopping the wallet and then restarting with the command line or configuration file option "--tx-new-billet-wait-sec=180". This will cause the wallet to wait 3 minutes for an expected incoming billet to clear before reporting "Insufficient funds".