Oh yeah I’ve seen this issue a lot! Idk why? However, I saw other uploaders place a “placeholder” after the last chapter they put up, as to stop these bots from re-uploading the chapters. Try doing that~
I think when only the first page is uploaded its cause the bot can't read the following format of the next pages (I might be wrong though), so it uploads only what it can.
It's happen again, who uploaded it? It's an anonymous uploader. I think it happened before where they didn't post the chapter :/