Yes, the extra entries are due to newly placing units in the scenario.
And right, there is no problem with the name. Some recent log entries from my ongoing test run:
...
2020-08-25 17:07:45 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening Luftwaffe/Units_50/Obst Teuffel.bmp for reading
2020-08-25 17:07:45 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening Luftwaffe/Units_100/Obst Teuffel.bmp for reading
2020-08-25 17:09:53 pbedit.exe: [INFO ID 1] in Dib:ib(), opening American/Units/M-8 HMC-.bmp for reading
2020-08-25 17:09:53 pbedit.exe: [INFO ID 1] in Dib:ib(), opening American/Units_100 - NATO/M-8 HMC-.bmp for reading
2020-08-25 17:09:53 pbedit.exe: [INFO ID 1] in Dib:ib(), opening American/Units_50/M-8 HMC-.bmp for reading
2020-08-25 17:09:53 pbedit.exe: [INFO ID 1] in Dib:ib(), opening American/Units_100/M-8 HMC-.bmp for reading
2020-08-25 17:09:57 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units/US HQ Recon Bn (mot).bmp for reading
2020-08-25 17:09:57 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_100 - NATO/US HQ Recon Bn (mot).bmp for reading
2020-08-25 17:09:57 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_50/US HQ Recon Bn (mot).bmp for reading
2020-08-25 17:09:57 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_100/US HQ Recon Bn (mot).bmp for reading
2020-08-25 17:11:02 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units/US Treadway Bridge (mot).bmp for reading
2020-08-25 17:11:02 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_100 - NATO/US Treadway Bridge (mot).bmp for reading
2020-08-25 17:11:02 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_50/US Treadway Bridge (mot).bmp for reading
2020-08-25 17:11:02 pbedit.exe: [INFO ID 1] in Dib:
ib(), opening American/Units_100/US Treadway Bridge (mot).bmp for reading
No slowdowns etc. from file reading those BMPs.