Possible reasons for DNA getting stuck in well
There is one simple reason for that, your agarose gel is most likely too dense. Depending in the type of agarose, I would prepare a 0.5-0.6% gel at maximum. 



Synbio gives this list for "standard" agarose, which fits pretty good with my experiences. If you use low melting agarose, this table looks a bit different, as the gel matrix is not a dense. The disadvantage is that the gel is much more prone to get damaged while handling.