Titanium http request leak - memory-leaks

Question

I have to make a load of subsequent http requests to load product images into the app as it has to function in an offline mode.
Around 2000 calls.
The http client seems toi have a memory leak which causes the persistent mbytes in "instruments" to rise to around 200 without being garbaged.
After use of the http client it is being set to null.
I have tried setting the file property of the httpclient without any success
I have set the unload function to only call the callback function which in turn calls the http send function again (thus looping through the 2000 products to get the respective pictures)
I changed from SDK 7.5.0.v20180824022007 to SDK 8.1.0.v20190423134840 and even SDK 9.0.0.v20181031080737 but the problem remains
the code of my http common module:
function HttpClient(options = {}) {
this.root = options.root || "ROOT_OF_API";
this.endpoint = options.endpoint || false;
this.needsChecksum = options.needsChecksum || false;
this.data = {};
this.method = options.method || "Post";
this.timeout = options.timeout || 5000;
this.calculateChecksum = function () {
var moment = require('alloy/moment');
if (!Alloy.Models.user.authenticated()) {
return false;
}
var sp = (moment().unix() - Alloy.Models.meta.get("timeDiff"))
var hash = Ti.Utils.md5HexDigest("nX" + sp + "FossilSFAapp" + Alloy.Models.user.get('token').substring(10, 14) + "CS")
var checksum = sp + "-" + hash.substring(4, 8)
this.data.checksum = checksum
}
};
HttpClient.prototype.setData = function (data) {
this.data = data
};
HttpClient.prototype.send = function (callback) {
// set new checksum for request if is needed
if (this.needsChecksum) {
this.calculateChecksum()
}
// add app version
if (this.method === "POST") {
this.data.appversion = Ti.App.version;
}
// send
var client = Ti.Network.createHTTPClient({
onload: function () {
callback({
success: true
})
},
onerror: function(e) {
callback({
message: e.messgae,
success: false
})
},
timeout: this.timeout
});
client.open(this.method, this.root + this.endpoint);
if (this.setFile) {
client.file = Ti.Filesystem.getFile(Ti.Filesystem.applicationDataDirectory, this.fileName);
}
client.setRequestHeader('Content-Type', 'application/json');
client.send(JSON.stringify(this.data));
client = null;
};
module.exports = HttpClient;
and then the module is used in the product model like so:
var HttpClient = require('./HttpClient');
var httpClient = new HttpClient();
function getImage (i) {
if (collection.at(i) && collection.at(i).get('iimage0') && collection.at(i).needsImageUpdate()) {
httpClient.endpoint = collection.at(i).get('acarticlenumber') +".jpg";
httpClient.fileName = 'productImages/' + collection.at(i).get('acarticlenumber') + '.jpg'
httpClient.send(function(e){
if (i < collection.length) {
i++
getImage(i)
} else {
finished()
}
});
} else {
if (i < collection.length) {
i++
getImage(i)
} else {
finished()
}
}
}
// start getting images at index 0
getImage(0)
anyone have an idea why these memory leaks appear ?
It only ever occurs when actually sending the http request.