They were JPG files as follows:
#1 951 KB @ 2520 x 1890 uploaded fine
#2 899 KB @ 3024 x 4032 would not upload (even by itself, as only Attachment) until I resized to 1890 x 2520
#3 2.08 MB @ 3024 x 4032 would not upload (even by itself, as only Attachment) until I resized to 1890 x 2520
Notice #2 smaller filer size than #1 but larger dimensions
php.ini:
post_max_size = 128M
upload_max_filesize = 16M
Forum permissions allow for 3 Attachments @ 16M each
