import re
regex = r"(?s):61:(?!.*:86:)(?:[\w /.-]|:(?!61:)[\w /.-]*)*"
test_str = ":61:2002190219C45612.4S202EXC:OL3654628815//CT56748005:86:/BENM/Unitech Imports/REM//58970.047:61:2002190219C30000S103LCADV5674920204//CT56748006:86:/BENM/Gravity Imports/REM//INV:/FEB20/446301:61:2002190219C45612.4S202EXCOL3654628825//CT56748005:60F:61:2002190219C45612.4S202EXCOL3654628815//CT56748018"
print(re.findall(regex, test_str))
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