Reproduceable 100% of the time in both Chrome and Firefox.

1. Pick either server to use a CD TOC with:
http://musicbrainz.org/cdtoc/attach?id=0zXouI8lyyAPSHpL2824yRHikyw-&tracks=8&toc=1+8+150448+150+17268+36744+56552+73172+93480+113786+130888&tport=8000
or
http://beta.musicbrainz.org/cdtoc/attach?id=0zXouI8lyyAPSHpL2824yRHikyw-&tracks=8&toc=1+8+150448+150+17268+36744+56552+73172+93480+113786+130888&tport=8000

Do a bogus search and enter the release editor.

2. Pick whether to put anything in Release Information. (doesn't matter)

3. Use the track parser with the following text: (tracks start with number, parse artists)
1 Beauty Boy 巧美(CV:福山潤)
2 On My Way 恒(CV:関智一)
3 冬空に願うだけ 貴世子(CV:寺崎彩乃)
4 盗人セレナーデ ラスティ・ネイル(CV:長弘翔子)
5 Beauty Boy(癒しのオルゴールVersion) 巧美(CV:福山潤)
6 On My Way(癒しのオルゴールVersion) 恒(CV:関智一)

(JIRA doesn't display this correctly. If you enter "Edit Issue", you can get the missing tab characters to paste into the track parser.)

Result:
1. It's not possible to add a 2nd row to any artist credit.
2. Try to edit the only artist credit on any row. It's not possible to select any entries in the in-line search.
3. Try to open the Track Parser. The button no longer does anything.