Problem with ligatures in case of many anchored objects

Hi!

I would like to ask help for a strange Indesign "bug" (sorry for my pure English!):

In order to be possible to write byzantine music (medieval greek) notation in Indesign, we have make a "plugin" that "reads" the musical notes (characters of a special opentype font named " Chourmouzes") and creates an anchored object (box) anchored before and placed under each of them, which (box) is going to be filled with the poetic text that corresponds to the specific note. In order to cover the huge variety of the musical characters, "Chourmouzes" has a lot of ligatures. But, when we began to test and use the plugin, we faced the following problem:

When the plugin creates all these anchored boxes, some of the ligatures of the font are being affected and the character of the ligature that has being typed last moves to another place.

For example, see below the positions of red characters depending on the number of anchored boxes:

Could anyone think a solution?

Thanks a lot!