Here is an example where targeting an internal exon of a pre-mRNA caused inclusion of the adjacent intron, an unusual outcome.
Vierstraete J, Willaert A, Vermassen P, Coucke PJ, Vral A, Claes KBM. Accurate quantification of homologous recombination in zebrafish: brca2 deficiency as a paradigm. Sci Rep. 2017;7:16518. doi:10.1038/s41598-017-16725-3
The oligo targeted zebrafish brca2 at the e7i7 junction. There are 28 exons in brca2-202, 27 exons in brca2-201 according to Ensembl ENSDARG00000079015 (accessed Nov 28 2017) .