Umm, trees can block signals.
Can you show us what the trees look like in the 227 direction? What does your antenna "see" in that direction?
If it is common to all channels, then it must be intermittent connection, intermittent interference, or intermittent interruption of signal path.
Do you have solar panels and an inverter?
ADTech's suggestion to simplify the system to isolate an intermittent connection is correct. Replace each component in the system with a known good component, until your simplified system is trouble free, even if it means substituting another antenna and ending up with a completely separate temporary independent system.
To check for interference, listen for noise on a portable radio on the AM broadcast band tuned to a vacant frequency first at the low end (540 kHz) and then at the high end (1600 kHz). If you hear noise on the AM broadcast band, there might also be noise on the TV bands. A radio that tunes the VHF aircraft band is also AM. An FM radio is not suitable for hunting noise, like power line noise.
While you are checking the signal strength on the TiVo diagnostics screen, also note the SNR and uncorrected errors readings.