Do you have a clear idea of where/which decryption library is failing?
Looking up for “decrypt” in dmesg/logcat I see nothing, and in recovery.log there is this part:
part of recovery.log when TW_INCLUDE_CRYPTO := true
I:Unable to mount '/data'
I:Actual block device: '/dev/block/sda11', current file system: 'f2fs'
I:Backup folder set to '/data/media/TWRP/BACKUPS/ef69ff96'
I:Settings storage is '/data/media'
DEBUG:prepdecrypt::Running prepdecrypt script for TWRP...
I:prepdecrypt::File Based Encryption (FBE) is present.
DEBUG:prepdecrypt::SDK version: 30
DEBUG:prepdecrypt::DEFAULTPROP variable set to prop.default.
DEBUG:prepdecrypt::A/B device detected! Finding current boot slot...
DEBUG:prepdecrypt::Current boot slot: _b
DEBUG:prepdecrypt::SETPATCH Override flag found.
DEBUG:prepdecrypt::Device has recovery partition!
DEBUG:prepdecrypt::Resetprop binary not found. Falling back to setprop.
DEBUG:prepdecrypt::Recovery/Fastbootd mode boot detected.
DEBUG:prepdecrypt::SETPATCH Override flag found.
I:prepdecrypt::SETPATCH=true
DEBUG:prepdecrypt::Build tree is Oreo or above. Proceed with setting props...
DEBUG:prepdecrypt::Temporary vendor folder created at /v.
DEBUG:prepdecrypt::vendor mounted at /v.
DEBUG:prepdecrypt::prepdecrypt.vendor_mounted=1
DEBUG:prepdecrypt::Vendor Build.prop exists! Reading vendor properties from build.prop...
DEBUG:prepdecrypt::Current vendor Android SDK version: 30
DEBUG:prepdecrypt::Current vendor is Oreo or above. Proceed with setting vendor security patch level...
DEBUG:prepdecrypt::Current Vendor Security Patch Level: 2127-12-31
E:prepdecrypt::setprop failed. Vendor Security Patch Level unchanged.
DEBUG:prepdecrypt::prop.default update successful! ro.vendor.build.security_patch=2021-12-05
DEBUG:prepdecrypt::System-as-Root device detected! Updating build.prop path variable...
DEBUG:prepdecrypt::Build.prop location set to system/build.prop.
DEBUG:prepdecrypt::Temporary system folder created at /s.
DEBUG:prepdecrypt::system mounted at /s.
DEBUG:prepdecrypt::prepdecrypt.system_mounted=1
DEBUG:prepdecrypt::Build.prop exists! Reading system properties from build.prop...
DEBUG:prepdecrypt::Current system Android SDK version: 30
DEBUG:prepdecrypt::Current system is Oreo or above. Proceed with setting OS Version & Security Patch Level...
DEBUG:prepdecrypt::Current OS Version: 11
DEBUG:prepdecrypt::setprop successful! New OS Version: 11
DEBUG:prepdecrypt::prop.default update successful! ro.build.version.release=11
DEBUG:prepdecrypt::Current Security Patch Level: 2127-12-31
E:prepdecrypt::setprop failed. Security Patch Level unchanged.
DEBUG:prepdecrypt::prop.default update successful! ro.build.version.security_patch=2021-12-05
I:prepdecrypt::crypto.ready=1
I:prepdecrypt::Script complete. Device ready for decryption.
Starting TWRP 3.6.0_11-0-bee26852 on Sat Feb 19 19:58:49 2022
(pid 638)
I:Lun file '/sys/class/android_usb/android0/f_mass_storage/lun0/file' does not exist, USB storage mode disabled
PRODUCT_USE_DYNAMIC_PARTITIONS := true
TW_INCLUDE_CRYPTO := true
The only error I see here is linked to the patch level (I guess?)
DEBUG:prepdecrypt::Resetprop binary not found. Falling back to setprop.
E:prepdecrypt::setprop failed. Vendor Security Patch Level unchanged.
E:prepdecrypt::setprop failed. Security Patch Level unchanged.
Then the prepdecrypt says it succeeded, but just after the device automatically reboot - and continue rebooting every 10 seconds. So strange 
I:prepdecrypt::crypto.ready=1
I:prepdecrypt::Script complete. Device ready for decryption.
Starting TWRP 3.6.0_11-0-bee26852 on Sat Feb 19 19:58:49 2022
(pid 638)