PLC IDE error: when program plc via LD, got error "An error encountered while drawing this network"

Hello

When program in ctrlX PLC (LD programming), when deleting a contact (picture_1), an error occours(picture_2), which can be reproduced under V12.9 and V1.16.0.

Error message: An error encountered while drawing this network, The contents cannot be displayed. 

Error occurs:

Is there anyone run into the similar trouble?