The length of page descriptions is controlled by a setting on the settings tab of the admin panel, in the "Search Settings" section. By default, "Maximum length of page summary displayed in search results" is set to 250.
There was a problem with version 126.96.36.199 (PDO) in which ANY change to the Sphider settings caused the description length to be either 0 or 1.
Later versions corrected the problem. However, if upgrading, the problem was fixed but the setting was not restored. Regardless, you may want to check that to be sure the description length is not 0. A related setting a few lines above the description length, ("The length of the description string queried from the database when displaying search results.") has a default of 0 (meaning unlimited) and if it is set to a very low number greater than zero, there may not be much in the way of a description.
Short answer, check you settings to be sure the query length is a decent number, or preferably, 0. Then check the description length to be sure it is not 0. The default is 250. If these values are correct, or resetting them to proper values does not correct the problem, check back and we can look at a couple other things to troubleshoot.
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