The files that you uploaded seem to contain the error already: After downloading again and opening unit.lfm in Notepad++ I see " Caption 'PikietaĹĽ 3 3.0.0.3'". Could you please upload the original (=correct) files?
And, please, don't use an external server, your files will be gone after a while and users visiting this thread later will not be able to load the project any more. Instead, use the "Attachments and other options" below the input field of the forum editor to upload the zip file to the forum. Remove the lib folder as well as any compiler-generated files from your zip, these files are not needed to compile the project and they will just blow up the upload size. Essentially, the zip should only contain pas, lfm, lpi and lpr files (plus some data files -- but this is not required in your case).
What happens if you create a new project with just a label containing Polish characters? Does it show the same problem?
Find out the directory which contains the Lazarus settings. In Windows 10 this is normally c:\Users\<your name>\AppData\Local\Lazarus. Or, if you have a secondary installation, you find the name of the settings folder in the file Lazarus.cfg in the directory containing Lazarus.exe. Close Lazarus, rename the settings folder and restart Lazarus again - this will create a new settings folder with original default settings. Does the error persist? (To restore the old settings just delete the new settings folder and rename the original one back).