Error while changing the Content Type of the request. How to eliminate?

Question

Ruby on Rails

There is a controller that processes requests from third-party systems.
As long as the requests went with the Content Type: text/xml header , there were no problems.
But when the requests changed Content Type: multipart/form-data - errors fell down, the request does not even reach the controller.

2022-04-01 17:47:50.002 ERROR --- [nio-8283-exec-7] o.g.web.errors.GrailsExceptionResolver   : FileUploadException occurred when processing request: [POST] /sou
the request was rejected because no multipart boundary was found. Stacktrace follows:

org.springframework.web.multipart.MultipartException: Could not parse multipart servlet request; nested exception is java.io.IOException: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found
        at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.parseRequest(StandardMultipartHttpServletRequest.java:116)
        at org.springframework.web.multipart.support.StandardMultipartHttpServletRequest.<init>(StandardMultipartHttpServletRequest.java:90)
        at org.springframework.web.multipart.support.StandardServletMultipartResolver.resolveMultipart(StandardServletMultipartResolver.java:81)
        at org.springframework.web.servlet.DispatcherServlet.checkMultipart(DispatcherServlet.java:1104)
        at org.grails.web.servlet.mvc.GrailsDispatcherServlet.checkMultipart(GrailsDispatcherServlet.groovy:75)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:936)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
        at org.springframework.boot.web.filter.ApplicationContextHeaderFilter.doFilterInternal(ApplicationContextHeaderFilter.java:55)
        at org.grails.web.servlet.mvc.GrailsWebRequestFilter.doFilterInternal(GrailsWebRequestFilter.java:77)
        at org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:67)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found
        at org.grails.web.filters.HiddenHttpMethodFilter.getHttpMethodOverride(HiddenHttpMethodFilter.java:71)
        at org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:60)
        ... 3 common frames omitted
Caused by: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found
        ... 5 common frames omitted

2022-04-01 17:47:50.004 ERROR --- [nio-8283-exec-7] .a.c.c.C.[.[.[.[grailsDispatcherServlet] : Servlet.service() for servlet [grailsDispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.web.multipart.MultipartException: Could not parse multipart servlet request; nested exception is java.io.IOException: org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found] with root cause

org.apache.tomcat.util.http.fileupload.FileUploadException: the request was rejected because no multipart boundary was found
        at org.grails.web.filters.HiddenHttpMethodFilter.getHttpMethodOverride(HiddenHttpMethodFilter.java:71)
        at org.grails.web.filters.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:60)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at java.lang.Thread.run(Thread.java:748)

Newbie in ruby. Don't scold too much.