emacs package hydra issue

[0x7FFFFFFFFFFFFFFF]

I've created an ascii recording at https://asciinema.org/a/7xfwpxzvfm6ozw662pcquicvi to show my issue with hydra. The description has been added to the video. Could anyone help me to take a look?

First I opened a file that has four lines of text. Then I selected all the text and use the command mc/edit-lines comes from multiple-cursors package to get 4 cursors (0:11). After that I use C-a to move those four cursors to the beginning of the lines (0:14). Then I use the command mc/insert-letters to insert letters at those cursor positions (0:19). As you can see, the characters a, b, c, d had been inserted (0:21). Then I repeated the command again to prove it works as expected (0:23). Then I use the command mc/insert-numbers to insert numbers to at the cursor positions (0:30) and it works. I executed this command again to prove it works as expected (0:37). After that I opened my init.elfile to show my configuration of hydra for multiple-cursors package (1:14) (please ignore my useless typings during this period, I'm not very good at emacs at the moment). As you can see in this configuration, I use C-t to trigger hydra, and use c to trigger mc/insert-letters, "i" to trigger mc/insert-numbers. Then I go back to the test file and use hydra to call those two functions. At 1:41, I successfully used hydra to get 4 cursors. Then I use c to insert letters (1:44). But as you can see, a, ba, cb, dc have been inserted into the beginning of the four lines respectively, which is not expected. Could you help to confirm if this is a hydra bug or my configuration problem? Thanks in advance my friend.