It is terrible that this is happening and the haven't bothered/been able to fix it.
For me, I occasionally get some unwanted bets because of this, but I still prefer this to how it was before when the bet slip was so sluggish, you had to start over from the beginning as soon as there was an odds change. So while I do get an unwanted bet here and here this is an improvement for me compared to how it used to be since I get more of my bets accepted these days. That being said, they should of course fix this bug.
The worst thing for me about their site is live odds not updating automatically. Often the odds that we see are inaccurate and we need to either try to place the bets or refresh manually to see updated odds. I've been pointing this out for close to two years now and more frequently since late last summer, but nothing has changed. On some days odds are updating fine, on others it's hit and miss and sometimes it's constantly bad.