Sorry I am not an experienced canning person. Try a Google search on “canning mistakes” or “canning errors”.

Anyone else have advice?

Very Cold - If you are in climate where the temperature in the garage will get below freezing so that the MRE gets frozen, the answer is it is not OK. Foods that contain meat should not be frozen thawed and re-frozen, it can make you ill. Freezing MRE once will not make it go bad, but it will degrade the nutritional value as much as 50% or more.

Very Hot - if you are in a climate where the temperature in the garage goes over 80 degrees Fahrenheit then the high temperatures will greatly diminish the shelf life of the MRE.

At 120 degrees storage temperature the MRE shelf life is only about one month,
at 100 degrees it will last almost 2 years,
at 80 degrees Fahrenheit, MRE shelf life will be over 6 years
below 70 degrees MRE shelf life will be 8-10 years.

So storing it in a garage for a few months one summer where daytime temperatures are over 100 degrees could make it go bad. It is better to store it in a basement rather then an un-air conditioned garage.

If you go on vacation and the basement temperature gets above in worst case 90 degrees for a few days it won’t significantly impact the shelf life of the MRE, as long as it not exposed to high temperature for months you can expect it to have at least 5 year shelf life if the temperature is below 80 degrees most of the year.