RxAndroidBle can connect to peripheral but standar

Question

Hoping that the experts might have a tip: I've inherited some code that uses the Android BLE API. It works OK with most devices, but will not connect to one, a blood pressure monitor. I wrote a quick test app using RxAndroidBle that connects fine as long as autoConnect is true. If it's false, I get an "already connected" error. With autoConnect true, I get the same error but after a few seconds it corrects itself and connects, then works as expected.

With the legacy code, the call to connect the device fails immediately with a DISCONNECTED state and a generic GATT_ERROR (status 0x85). This happens whether autoConnect is on or off.

Does this suggest any possible solution? (Unfortunately, rewriting the app isn't an option in the short term.) There's more info here: