This is a known issue of some of the caches. But as explained in the FAQ, there is usually nothing you can do about that:
http://project-gc.com/Home/FAQ#2384662308
We do not do manual changes in the data. But if you find an entry that seems to be off by a lot more than in other services, feel free to report it so that we can investigate.
But in your example, it looks like there is really something terribly wrong, because query on
http://www.gpsvisualizer.com/elevation
Coordinates (lat,lon): (34.85878 33.25958) FIND ELEVATION → 425 meters (1396 feet) [data source: SRTM1]
That is a source, that should be used by PGC too. So this is something that ganja1447 should investigate further.