Weird Sharepoint 2019 search issue

We have Sharepoint 2019 on premise. We just found a strange search issue. Hope I can get some idea how to pin down the cause.

So user uploaded two files, one has title DriveCA Input Tool User Guide, name is DriveCA_Input_Tool_User_Guide.pdf, another file has same title, but file name is DriveCA_Input_Tool_User_Guide_2018.pdf.

When search "DriveCA Input Tool User Guide", user only got DriveCA_Input_Tool_User_Guide_2018.pdf. After I did a full crawl, user can only got DriveCA_Input_Tool_User_Guide.pdf.

So I tried to figure out the cause, I change the title of the 2018 file from "DriveCA Input Tool User Guide" to "DriveCA Input Tool User Guide 2018" so I can distinguish the two, also to avoid the hide duplicate mentioned in some article. I then found a interesting thing, when I search Title:"DriveCA*", I can only get the "DriveCA Input Tool User Guide" file. Even I tried Title:"DriveCA*2018" I cannot get the 2018 file. But if I search Title:"DriveCA Input Tool User Guide 2018", I can get the 2018 file.

Any idea?