We have been able to reproduce this issue when using two reflection probes, one larger and one smaller, which overlap but not fully. In this case, this behavior is by design and the issue can be easily resolved. If you are working with multiple reflection probes, can you make sure that the larger one fully encompasses all the smaller ones and see if that solves your issue? You can do that by increasing the bounds of the outer reflection probe.
If you are not working with multiple overlapping reflection probes, we have not been able to reproduce the issue using only the default skybox probe, so if this is the case we will need a repro project and instructions on how to reproduce the issue. You can find instructions on how to file this bug report here.