Black Tank Leak - questions

For the sake of clarification, the original damage to the tank was done by the previous owner backing up over a concrete planter box. The leak was severe. It was approximately 8 to 10 inches long and around 3/4 of an inch wide in one area where a piece of the plastic fell out. Eventually, I repaired the crack with two layers of glass cloth soaked in epoxy resin. I scraped everything clean for three inches all the way around and really roughed up the surface with 36 grit sanding cloth before the repair. In the two months since this repair we have been through temperatures as low as 18 degrees and as high as 90 degreeS with no problems. I've filled the tank to capacity at least five times just to make sure the patch was holding. I feel pretty secure with the repair and I honestly doubt that it could have been accomplished any better given the circumstances. We live in this trailer full time and don't have the luxury of time or the equipment necessary to drop the tank for welding, let alone to redesign the tank's suspension.
The secondary leak did not come from the repaired area and there are no other indications of any leakage. The secondary leak amounted to about a gallon of nearly clear water and it came from above the plastic tank, not the tank itself. In the last five weeks the problem has not been repeated.
It may have been a backup into vent line or just something caused by all of the rain lately, but it hasn't happened again and I am not inclined to look for problems that cease to be problems. I appreciate all of the good ideas and advice that has been offered here, but for the time being I think I will walk over to the lake and do some fishing. Thank you.