FYI, I reported the following issue to Tile5 project:
"multiple ImageMarker are not always drawn"
https://github.com/sidelab/tile5/issues/#issue/51
Hope that helps.
Looks like your latest changeset correct this issue:
https://github.com/sidelab/tile5/commit/a83ddd8f7a9fb40b286419aca4c15527624367c5
See:
http://playground.mekensleep.com/~proppy/tile5markerbugfix/