Intermittently we receive the "Required Tag Missing" error for existing fields

Hello QuickFix support,

Could you advise on the following issue, please?

We receive intermittent "Required Tag Missing" error while parsing incoming fix messages, even though the missing field is present in the message. For example in the following message the tag 447 is present on the message, and yet sometimes we receive “Required Tag Missing, field=447” while parsing it.

8=FIX.4.4|9=284|35=F|49=TEST_49|56=TEST_56|34=420|52=20190302-07:31:57.079|115=TEST3|116=TEST_116|11=TEST_11|41=TEST_41|55=TEST_55|48=TEST_48|22=4|54=2|60=20190302-07:31:56.933|38=TEST_38|207=TEST_207|454=3|455=TEST_455_1|456=TEST_456_1|455=TEST_455_2|456=TEST_456_2|455=TEST_455_3|456=TEST_456_3|453=1|448=TEST_448|447=D|452=3|10=XXX|

This issue has been observed with cancel messages and it normally happens after application startup. We do use a data dictionary, and 99.8% of the time such cancellation messages work fine. We use quick fix version 1.5.3. (quickfixj-core-1.5.3.jar and quickfixj-msg-fix44-1.5.3.jar)

Could you take a look at it?

Many thanks
Michael