sed - multi-line replace and combine - sed

Question

I have the following sed code below that takes a number of lines and concatenates that them into one, while removing un-wanted data.
Here sed captures everything between the lines starting with To: and ending with X-RSMF-Generator, in addition, it also catutres everthign between the line starting with X-RSMF-Participants: and ending with MIME-Version
#!/bin/sh
#Sed turotial
shopt -s nullglob
FILES=/mnt/c/Temp/rsmf/*.rsmf
for f in $FILES
do
FileName=$f
#echo "$FileName"
#echo "Processing $f
sed -rn \
-e '/^To/,/X-RSMF-Generator:/{
#s/To: //
s/X-RSMF-Generator:.*/_/
s/\r\n//g
H
}' \
-e '/^X-RSMF-Participants:/,/^MIME-Version/{
s/X-RSMF-Participants: /_/
s/MIME-Version.*//
H
G
s/\r\n//gp
}' \
$f
done
Sample Data
To: Person One <>, "Person two" <person.two#gmail.com>, ,
"Person Three ***" <>
X-RSMF-Generator: Relativity RSMF Generator Sample Library
X-RSMF-Version: 1.0.0
X-RSMF-EventCount: 53
X-RSMF-BeginDate: 2022-09-20T04:33:11-04:00
X-RSMF-EndDate: 2022-09-20T16:47:56-04:00
X-RSMF-GroupID: GRP000000118
X-RSMF-SecondaryGroupID: GRP000000118_D_20220920
X-RSMF-ContainsDeleted: False
X-RSMF-Application: Native Messages
X-RSMF-Participants: Person eight <5148842954> next person available.
<Email.one#gmail.com> <342453136512> Next Person *** <9876582694>
<first.man#gmail.com> <888888889> Second Man *** <9999999999>
<fourth.man#gmail.com> <444444444> Thrid Man *** <3333333333>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="=-D+MPqNoS/tGpx2q22uID4A=="
Results
_Person eight <5148842954> next person available.
To: Person One <>, "Person two" <person.two#gmail.com>, , "Person Three ***" <>
_Person eight <5148842954> next person available.
<Email.one#gmail.com> <342453136512> Next Person *** <9876582694>
To: Person One <>, "Person two" <person.two#gmail.com>, , "Person Three ***" <>
_Person eight <5148842954> next person available. <Email.one#gmail.com> <342453136512> Next Person *** <9876582694>
<first.man#gmail.com> <888888889> Second Man *** <9999999999>
To: Person One <>, "Person two" <person.two#gmail.com>, , "Person Three ***" <>
_Person eight <5148842954> next person available. <Email.one#gmail.com> <342453136512> Next Person *** <9876582694> <first.man#gmail.com> <888888889> Second Man *** <9999999999>
<fourth.man#gmail.com> <444444444> Thrid Man *** <3333333333>
To: Person One <>, "Person two" <person.two#gmail.com>, , "Person Three ***" <>
_Person eight <5148842954> next person available. <Email.one#gmail.com> <342453136512> Next Person *** <9876582694> <first.man#gmail.com> <888888889> Second Man *** <9999999999> <fourth.man#gmail.com> <444444444> Thrid Man *** <3333333333>
To: Person One <>, "Person two" <person.two#gmail.com>, , "Person Three ***" <>
_Person eight <5148842954> next person available. <Email.one#gmail.com> <342453136512> Next Person *** <9876582694> <first.man#gmail.com> <888888889> Second Man *** <9999999999> <fourth.man#gmail.com> <444444444> Thrid Man *** <3333333333>
There are a few issues I am encountering is
The first lines does not concatenate with the second.
in the second capture, each time a new line is read, it adds it to the buffer and the line is printed each time. although the print command is only list once. I also not sure why the last line is printed twice. I am sure am missing something simple.
i am also looking for a method of printing the filename of the file being read at at the beginning of the line two know where the date came from as i have thousands of files.
assistance is greatly appreciated, thank you in advance.