"Illegal repetition near index" Error in Flow Ask for Approval ActionIssue <!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } The following (or similar) error message is displayed in the Flow execution details or logs: Illegal repetition near index 2 in pattern ^{C}{Y}C\d{8,}$ The issue is happening when certain numbering configurations are used. Release<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } All Cause<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } The issue is caused by invalid regular expression (regex) patterns defined in the sys_number.prefix field. The sys_number table is responsible for managing numbering rules across the system. One of its key fields, prefix, defines the string pattern that is prepended to generated numbers. In this case, special characters such as {C}{Y} were used directly in the sys_number.prefix field. These characters are interpreted as regex quantifiers, resulting in an invalid regex pattern and causing the runtime error. Important Notes on sys_number.prefix The prefix is optional and can be left blank.If used, it must contain only alphanumeric characters (A–Z, a–z, 0–9).Special characters are not allowed, including but not limited to: / \ ! @ # $ % ^ & * ( ) - + ’ ” : ; < > , . { } [ ] Invalid regex patterns in the prefix can break dependent processes, including the Ask for Approval Flow action. Resolution<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } Update the sys_number.prefix field to ensure it contains only valid alphanumeric characters and does not include special characters. Removing or correcting the invalid prefix will prevent the regex error. If the business requirement mandates the use of special-character-like patterns (for example {C}{Y}C), the prefix can be stored as a valid escaped regex, and then parsed in script logic. For example: Use escaped characters in the sys_number.prefix value: \\{C}\\{Y}C This makes the prefix a valid regex. Then, in the related Business Rule (BR) or script, remove the escape characters before using the value. Sample Script Change let unparsedPrefix = "\\{C}\\{Y}C"; // input stringlet prefix = unparsedPrefix.replace(/\\/g, ""); // remove all backslashesconsole.log(prefix); // {C}{Y}C This approach minimizes changes to existing Business Rules while avoiding regex errors. ImportantCustomers should thoroughly test the modified script in a non-production instance before applying it to production.