Re: Missing last modification info. Is this causing crawling problems ?

I've noticed a similar problem.

It seems that each time the sitemap is manually submitted (via the
Resubmit Selected button) the past progress Googlebot made on the
sitemap is erased and it starts indexing the site from scratch.

I had to resubmit the sitemap because the site went down for a few
hours due to a problem node and Googlebot tried to fetch it during that
time and failed, resulting in an Sitemap Status error. The instructions
given in the FAQ recommended resubmitting the sitemap, which I did.
Before that time, Googlebot had successfully indexed 101 pages which
were showing up in Google. After the sitemap was resubmitted, it
dropped back down to zero.

Are there any solutions available to prevent this from happening again?