Importing new photos that Lightroom says I already imported

Just recently incounter this problem for me not sure will it work for you all but here's my solution 

Step 1: Go to Recently Added 
Step 2: Check if there's any existing photo that inside you've might import into (Even if we delete it from the album side lightroom might still save into it's system)
Step 3: Select your desired photo to delete it 
Step 4: Import your photo that you wanted 

This works for me quite well hope it helps some of you all!

I recently had this problem and after a lot of searching around, this is what worked for me. 

I went to the "By Date" section and found the files which had the same filenames of the ones I was trying to add and right clicked and selected Delete.

After this I was able to add the new ones.

I just encountered and overcame this bug. Here is exactly what I did to fix it, and I can confirm it worked. What follows are instructions for the Apple environment... 

1. I opened the original files in Finder, and confirmed their location

2. I batch renamed the files using Adobe Bridge (open Bridge; in the Folders section, locate the folder with your pictures; ensure the pictures are shown in the Content section, then click Workflow, create a new Batch Rename workflow, add a sequence number).

3. The copied files are then found in a new subfolder of the original locations, called Workflow. 

4. Inside Lightroom Library, click import, and reimport the files in the Workflow folder into your Library. 

5. Finally, I located the partial folder in my Library and removed it using Control+click > Remove.

4 years later.. bug still there..