The most likely cause is a fault in the lens, not the camera body. Since it only happens as the lens extends toward 300mm, a connection is probably being disturbed mechanically at longer extension.

Two plausible possibilities from the symptoms:

• the lens mount/rear flange connection is slightly loose, so extending the lens changes the fit enough to interrupt communication
• an internal electrical connection inside the lens is failing or being stretched at the long end

The overexposed frames strongly suggest the aperture may not be stopping down correctly. For example, if the camera commands f/11 but the lens stays near wide open, the result would be much brighter than expected.

A useful check is to compare shots at wide open versus stopped down apertures, especially near 300mm. If wide-open shots work more reliably but stopped-down shots become overexposed or trigger the error, that supports an aperture/control connection fault inside the lens.

So yes—this behavior is consistent with a lens communication or aperture-control problem that appears only at certain zoom positions. The lens likely needs inspection/repair, with special attention to mount fit and internal flex/contact issues.