* paste in **D2** cell and drag down:

 <b><pre><code>=ARRAYFORMULA(TEXTJOIN(", ", 1, REGEXREPLACE(TRIM(IFERROR(SPLIT(B2, ","))), 
     TEXTJOIN("|", 1, IF(REGEXMATCH(TRIM(IFERROR(SPLIT(B2, ","))), 
     TEXTJOIN("|", 1, TRIM(IFERROR(SPLIT(C2, ","))))), 
     TRIM(IFERROR(SPLIT(B2, ","))), )), TRIM(IFERROR(SPLIT(B2, ",")))&" - CHECK")))</code></pre></b>

 [![0][1]][1]

__________

<b><pre><code>=ARRAYFORMULA(SUBSTITUTE(SUBSTITUTE(TRIM(TRANSPOSE(QUERY(TRANSPOSE(SUBSTITUTE(IF(ISNUMBER(
 QUERY(QUERY(IFERROR(SPLIT(IF(IF(REGEXMATCH(TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(
 TRANSPOSE(IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), )))
 ,,999^99)),,999^99), "♠"))),SUBSTITUTE(TRIM(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(
 SPLIT(C2:C, ",")<>"", A2:A&"♦"&TRIM(IFERROR(SPLIT(C2:C, ","))), ))),,999^99)),,999^99))
 , " ", "|")), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(
 SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), ))),,999^99)),,999^99),
 "♠")))&" - CHECK", )<>"", IF(REGEXMATCH(TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(
 IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), )))
 ,,999^99)),,999^99), "♠"))),SUBSTITUTE(TRIM(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(
 SPLIT(C2:C, ",")<>"", A2:A&"♦"&TRIM(IFERROR(SPLIT(C2:C, ","))), ))),,999^99)),,999^99)),
 " ", "|")), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(
 SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), ))),,999^99)),,999^99), 
 "♠")))&" - CHECK", ), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(
 SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), ))),,999^99)),,999^99),
 "♠")))), "♦")), "select count(Col1) where Col1 is not null group by Col1 pivot Col2", 0), 
 "offset 1", 0)), INDEX(QUERY(IFERROR(SPLIT(IF(IF(REGEXMATCH(TRIM(TRANSPOSE(SPLIT(QUERY(
 TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(
 SPLIT(B2:B, ","))), ))),,999^99)),,999^99), "♠"))),SUBSTITUTE(TRIM(QUERY(TRANSPOSE(QUERY(
 TRANSPOSE(IFERROR(IF(SPLIT(C2:C, ",")<>"", A2:A&"♦"&TRIM(IFERROR(SPLIT(C2:C, ","))), )))
 ,,999^99)),,999^99)), " ", "|")), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(
 IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), )))
 ,,999^99)),,999^99), "♠")))&" - CHECK", )<>"", IF(REGEXMATCH(TRIM(TRANSPOSE(SPLIT(QUERY(
 TRANSPOSE(QUERY(TRANSPOSE(IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(
 SPLIT(B2:B, ","))), ))),,999^99)),,999^99), "♠"))),SUBSTITUTE(TRIM(QUERY(TRANSPOSE(QUERY(
 TRANSPOSE(IFERROR(IF(SPLIT(C2:C, ",")<>"", A2:A&"♦"&TRIM(IFERROR(SPLIT(C2:C, ","))), )))
 ,,999^99)),,999^99)), " ", "|")), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(TRANSPOSE(
 IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), )))
 ,,999^99)),,999^99), "♠")))&" - CHECK", ), TRIM(TRANSPOSE(SPLIT(QUERY(TRANSPOSE(QUERY(
 TRANSPOSE(IFERROR(IF(SPLIT(B2:B, ",")<>"", "♠"&A2:A&"♦"&TRIM(IFERROR(SPLIT(B2:B, ","))), )))
 ,,999^99)),,999^99), "♠")))), "♦")), "select count(Col1) where Col1 is not null group by Col1 
 pivot Col2", 0), 1, ), ), " ", "♀")),,999^99))), " ", ", "), "♀", " "))</code></pre></b>

[![0][2]][2]


  [1]: https://i.sstatic.net/Lf217.png
  [2]: https://i.sstatic.net/Z1g5f.png