Yea PB, what causes the diminished ability to effectively "repair" damage post injury involves ALL areas of synthesis but protein modulated recovery is particularly venerable.
Why? The same mechanisms that are responsible for AGING, the inability of DNA to correct deletion or substitution nucleotide insertions. The net effect is a "weak chain in a link" literally.
Yep DNA is indeed far from perfect and errors occur every second literally BUT most are removed with a correct sequence inserted. However the ability to correct for defects diminishes with age. The process slows at around age 30 and accelerates remarkably by age 60-65.
jim