signs blockdata glitched

signs modified by /blockdata in 1.8 and opened in the 1.9 snapshots show null on lines that should be empty. running the /blockdata command again from the command blocks that modified it first shows part of the command instead of the text i was expecting. happened even when i removed all commas from the command

i expected the signs to look the same as in 1.8 and the running the command again to fix any glitches.

when i opened my pvp arena in 1.9 the signs showed null on empty lines and the command did not work.