The site of label is wrong

[hyzhou1990]

Describe the bug
In some situation, the wrong placement of label on the tree may caused the wrong fixation results.

A clear and concise description of what the bug is.

To Reproduce

The tree and sequence alignment file are needed in most cases to reproduce the bug, you can either:

1. Use upload the tree and sequence alignment file.
2. Or the saveRDS function to save the R object causing the bug and upload the RDS file.
3. If the file(s) exceeds the size limit, email those file(s) to [email protected].

Screenshots

Version info:

Run sessionInfo() in the R console and paste the output below.