You mentioned “trees” across the street. How tall are they? And how dense and thick are they? What is the distance of those trees from the front of the antenna in the attic?
If the RF 42 is doing occasional “short burst multi-path”, like a few or several times a minute plus or minus; then it is very likely the trees and possibly the office building might simply increase the occurrence of the multi-path, if it has any affect at all.
If you have any type of signal meter in the TV or DVR or other device; then the short burst multi-path should be visible by watching the meter pop “up” and “down”, like a yo-yo.
If this is short burst multi-path, and if it is caused by the trees, and/or the interaction with the buildings, then often just moving the antenna about 3 feet can make a big difference for RF's 30-45. This includes moving the antenna to a much lower position. Some trees like very large oak and pecan, you may get a solid signal at just 5 foot off the ground, but the signal could be blocked 25 foot above the ground because of the trees.