I'm both happy and depressed to have finally found this thread.
Happy because I've been having the same problem for months and this is the first time I've seen it flagged.
And depressed because there is no solution and even worse nothing from Apple on fixing, nor even acknowledging the issue.
Like JohnnyW2001 posted earlier, the only thing I've found that helps is uninstalling Chrome and blocking the App Store app.
However, when my son needs a new app and I've allowed the App Store to get it, I often forget to block it again.
And then later on I find him on his phone after the time restrictions and realise he's downloaded Chrome again to get around them!