@teratronic
With headless devices (no screen keyboard), I advise you to look and do what is proposed here : How to Run a pfSense Software File System Check
This one Upgrading pfSense Software contains also useful information.
Both are Netgate video's. These guys know what they talk about : they created the devices.
What we all do wrong, just to gain several minutes, and loosing hours afterwards as a result :
Before thinking of upgrading :
Check free disk space. Do so using console or SSH access.
Check if, during the boot cycle, there are no mount errors (see first video).
Check that you have a local (USB) copy of the current config.xml.
Check that you have a copy of the current version of pfSense ready on a USB.
Because you have multiple devices, you can easily test faulty PSU's. Bit be careful : bas PSU's can do harm to the disk : not physical, but on a written 'bit' level. On the next boot, your device refuses to boot ...
For any pfSense, a good PSU is import. As important as a good UPS.
An UPS is not mandatory, an UPS is only important if your internet connection is important to you.