Based on the available reports, yes—this appears to be normal behavior on the Canon EOS 750D. Changing shooting modes can cause the camera’s Wi‑Fi session to end, so the phone app disconnects and must reconnect afterward.

From the answers provided, there isn’t a known setting or workaround that reliably prevents this on the 750D. The practical options are:

• set your shooting mode before starting the Wi‑Fi session
• reconnect after changing modes
• check whether a Canon firmware update improves behavior

So, unfortunately, this is most likely an intended limitation of how Wi‑Fi works on that camera rather than a fault with your phone or app.