MeteorJS server crash complaining Error: ENOENT: no such file or directory, open '..../cfs/files/_tempstore/..chunk' - heroku

Question

Recently, we created a new upload image/PDF function.
When someone uploaded a PDF, the server still worked. But after a daily restart, the server kept crashing:
2022-05-25T00:52:13.648659+00:00 app[web.1]: (node:3) [DEP0005] DeprecationWarning: Buffer() is deprecated due to security and usability issues. Please use the Buffer.alloc(), Buffer.allocUnsafe(), or Buffer.from() methods instead.
2022-05-25T00:52:13.747819+00:00 app[web.1]: internal/streams/legacy.js:61
2022-05-25T00:52:13.747821+00:00 app[web.1]: throw er; // Unhandled stream error in pipe.
2022-05-25T00:52:13.747821+00:00 app[web.1]: ^
2022-05-25T00:52:13.747821+00:00 app[web.1]:
2022-05-25T00:52:13.747822+00:00 app[web.1]: [Error: ENOENT: no such file or directory, open '/app/.meteor/heroku_build/cfs/files/_tempstore/retailerRegistrationMedia-w6e6Kxgy8QLTgirET-0.chunk'] {
2022-05-25T00:52:13.747822+00:00 app[web.1]: errno: -2,
2022-05-25T00:52:13.747823+00:00 app[web.1]: code: 'ENOENT',
2022-05-25T00:52:13.747823+00:00 app[web.1]: syscall: 'open',
2022-05-25T00:52:13.747835+00:00 app[web.1]: path: '/app/.meteor/heroku_build/cfs/files/_tempstore/retailerRegistrationMedia-w6e6Kxgy8QLTgirET-0.chunk'
2022-05-25T00:52:13.747836+00:00 app[web.1]: }
Investigating further, it appears that if we delete last record from the cfs._tempstore.chunks collection, the server can then starts correctly.
Also, the crash ONLY happens, if the uploaded media is a PDF. No crash if uploaded media is image
What is the cause of this error?
Relevant code to save an image below:
Meteor.utilities.addRetailerRegistrationMediaFile(e, function(fileId){
if(e.target.id == "companyACRAFile"){
tpl.companyACRAFile = fileId;
}else if(e.target.id == "companyShopPhotos"){
tpl.companyShopPhotos.push(fileId);
console.log("tpl.companyShopPhotos", tpl.companyShopPhotos);
}
});
Meteor.utilities.addRetailerRegistrationMediaFile = function (e, callback) {
var $target = $(e.currentTarget)
FS.Utility.eachFile(e, function (file) {
RetailerRegistrationMediaObjects.insert(file, function (err, fileObj) {
if (err) {
return throwError(err);
}else{
callback(fileObj._id);
}
});
});
};
// For all retailer application media
RetailerRegistrationMediaObjects = new FS.Collection("retailerRegistrationMedia", {
stores: [
new FS.Store.S3("registrationThumbs", {
region: settings.public.aws_region,
accessKeyId: settings.public.aws_key_id,
secretAccessKey: settings.public.aws_access_key,
bucket: settings.public.aws_bucket,
folder: "registration/thumbs",
transformWrite: createThumbIfImage,
}),
new FS.Store.S3("registration", {
region: settings.public.aws_region,
accessKeyId: settings.public.aws_key_id,
secretAccessKey: settings.public.aws_access_key,
bucket: settings.public.aws_bucket,
folder: "registration",
}),
],
filter: {
maxSize: 5000000, //in bytes
allow: {
contentTypes: ["image/*", "application/pdf"],
},
onInvalid: function (message) {
if (Meteor.isClient) {
// prepare the data for notification
sAlert.error(message);
}
},
},
});
RetailerRegistrationMediaObjects.allow({
insert: function (userId, doc) {
return true;
},
update: function (userId, doc, fieldNames, modifier) {
return true
},
remove: function (userId, doc) {
return true
},
download: function (userId) {
return true;
},
});