Unwanted IR remote control interaction

Assuming a ground state where all units were powered off and the Roku was disconnected and reconnected to its power source, on power up the cable box output works fine through the AV system/receiver to the TV. All cable functions accessible through the cable box remote control work as expected. The AV system/receiver remote control works as expected.

The system is configured so the Roku can be switched in using the AV system/receiver remote by selecting 3D/DVD on the remote. When selected, the Roku and its remote function as expected.

Problems arise when I switch to the cable box after the Roku has been used. Certain buttons on the cable box remote, such as the channel select and page up/down buttons, will cause the AV system/receiver to switch back to the Roku. Switching the cable box back in using the AV system/receiver remote, is effective but the cable box remote will still switch the AV system/receiver to the Roku as described above.

The only remedy for the AV system/receiver and cable box to function is to power down the Roku for a few seconds to regain normal control functions till the next time I change inputs.

Is there a fix?

Cable box: Motorola DCX3501-M

AV System/Receiver: Sony STR-DH520

Roku Express: 3930X

TV: Sanyo

Cable provider: Spectrum/Charter