OOB carrier is usually a QPSK modulated channel, so the SNR requirements are much lower than a 256QAM video or modem channel.
QPSK channel SNRs are usually recommend to be 15 dB or above as good, but down to 12 is usable but it may have errors.
With your OOB being at 89.5 mhz, it's prone to interference with FM signals (88-108 Mhz). Make sure all the connectors in your home are tight and the cable through out the house is undamaged.--
If it's important, back it up... twice. Even 99.999% availability isn't enough sometimes.