Hello
we would like to ask you a simple help and advice for our forum and your question: do yourself a favour and please read How to get the best out of this forum and post accordingly (including code with code tags).
Accordingly please correct your post and add code tags around your code.
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To your question, the extreme values suggest a wiring or configuration fault on the MAX31865, but using software SPI with six devices can also cause unstable reads on an ESP32, especially when WiFi is active, so hardware SPI is preferable. The choice of CS pins (notably GPIO 2 and 15) could be an issue on some ESP32 (unstable boot or behavior depending on pull states) and the 2.5 s blocking delay can further destabilize operation and break Blynk synchronization.