/* istanbul ignore next */ comments breaking snapshots in Jest / Vue tests

I'm running some VueJS tests in a circleCI pipeline and it's failing a snapshot for a difference on a vue-select dropdown:-

- Snapshot
+ Received

@@ -77,12 +77,12 @@
          >
            <vue-select
              label="description"
              options=""
              reduce="function (option) {
-           /* istanbul ignore next */cov_k4ut4ymr5.f[9]++;
-           cov_k4ut4ymr5.s[34]++;
+           /* istanbul ignore next */cov_2541t4fi73.f[9]++;
+           cov_2541t4fi73.s[34]++;
            return option.id;
          }"
            />
          </div>
           
@@ -127,12 +127,12 @@
          >
            <vue-select
              label="description"
              options=""
              reduce="function (option) {
-           /* istanbul ignore next */cov_k4ut4ymr5.f[9]++;
-           cov_k4ut4ymr5.s[34]++;
+           /* istanbul ignore next */cov_2541t4fi73.f[9]++;
+           cov_2541t4fi73.s[34]++;
            return option.id;
          }"
            />
          </div>

I don't really understand what's causing this but there clearly are differences. This doesn't fail when I run the tests locally. Do I need to add some config around the istanbul plugin perhaps?