Thank you very much.
I tested it and found another problem.
If I mix 1-byte and 2-byte characters in the values of radio buttons and checkboxes, they are not output.
Also, a combination of 2-byte characters and some 2-byte symbols will not be output.
The test code used for the ‘Contact form 7’ form is as follows:
1. Radio button 1-byte characters and 2-byte symbols: [radio radio-1_2 use_label_element default:1 "180°" "2-byte spaces"]
2. Radio button 2-byte characters and 2-byte symbols: [radio radio-2_2 use_label_element default:1 "全角スペース ←ここ" "全角(括弧)"]
3. Checkbox 1-byte characters and 2-byte symbols: [checkbox checkbox-1_2 use_label_element "37℃" "全角括弧と数字(123)" "2-bite space"]
4. Checkbox 2-byte characters and 2-byte symbols: [checkbox checkbox-2_2 use_label_element "全角 スペース" "全角(括弧)"]