Hello,
We didn’t change anything in last update that could make any changes for off-canvas sidebar so we consider the main reason of the issue could be in caching on your web-site. Could you check without caching plugins or if you have caching on your server then contact with your server support to disable caching and check again. If the reason is in caching then you should ask plugin’s/hosting how make it compatible with mobile version. I think that main issue could be in working of wp_is_mobile() that is official WP function but many cache plugins have issues with it. Remind one more time that we did no changes in latest update that caused such issue so it is a local issue.
Regards